An 8.9-magnitude earthquake hit northern Japan early Friday, triggering tsunamis that sent a wave filled with boats and houses toward land. Are you in an affected area? Send an iReport. Read the full report on how the quake hit Japan and generated a Pacific-wide tsunami.

[10:30 p.m. ET, 12:30 p.m. Tokyo] The 15-member Chinese rescue team is bound for the quake-hit region in Japan. The team's main task was to search for survivors, Yin Guanghui, deputy director of the China Earthquake Administration, said. The members of the Chinese International Search and Rescue are bringing four tons of materials and equipments for search and rescue as well as power supply and telecommunication services, Yin said.

[10:20 p.m. ET, 12:20 p.m. Tokyo] The death toll has climbed to 763. There are 639 missing and 1419 injured, according to Japan's national police agency.

[9:54 p.m. ET, 11:54 a.m. Tokyo] A meltdown may have occurred at at least one nuclear power reactor in Japan, the country's chief cabinet secretary, Yukio Edano, said Sunday.

He also said that authorities are concerned over the possibility of another meltdown at a second reactor.

"We do believe that there is a possibility that meltdown has occurred. It is inside the reactor. We can't see. However, we are assuming that a meltdown has occurred," he said of the No. 1 reactor at the Fukushima Daiichi nuclear facility. "And with reactor No. 3, we are also assuming that the possibility of a meltdown as we carry out measures."

Edano's comments confirm an earlier report from an official with Japan's Nuclear and Industrial Safety Agency, who said, "we see the possibility of a meltdown."

A meltdown is a catastrophic failure of the reactor core, with a potential for widespread radiation release. However, Toshihiro Bannai, director of the agency's international affairs office, expressed confidence that efforts to control the crisis would be successful.

[9:35 p.m. ET, 11:35 a.m. Tokyo] A woman trapped in a secure building in downtown Sendai made a tearful plea to the world for help.

"Somehow, we can hang in there, I hope. We don't have any electric, water, gas... but please, help the people who lost their homes and the people on top of the buildings asking for help," Yasue Schumaker told CNN.

"We need foreign countries' help," she said, choking back tears. "We're in an emergency, please help us."

At least 49 countries and the European Union have offered relief to Japan, and supplies and personnel are on the way.

Schumaker, a resident of Hawaii originally from Sendai, had been visiting her hometown to care for her ailing mother.

Schumaker said people were too afraid to leave the building and no one knew when to expect help. Outside, she said she saw people sleeping in cars, perhaps reluctant to leave the safety of their vehicles for the cold weather.

[9:10 p.m. ET, 11:10 a.m. Tokyo] The U.S. State Department will on send a consular support team into the Sendai area near the earthquake's epicenter on Sunday, while adding personnel to the U.S. Tokyo embassy in an effort to aid American citizens. Ten U.S. Naval ships are bound for Japan carrying humanitarian aid and emergency crews in effort to aid in disaster relief, Anthony Falvo, a U.S. Navy Public Affairs Officer, said.

The nuclear-powered aircraft carrier USS Ronald Reagan, along with a guided-missile cruiser and destroyer ship, arrived off Japan's coast Sunday morning to support Japanese forces in disaster relief operations, the U.S. Department of Defense said in a statement.

[8:47 p.m. ET, 10:47 a.m. Tokyo] A state of emergency has been declared for three reactors at the Fukushima Daiichi nuclear power plant. Roughly 180,000 people who live within 10 to 20 kilometers of the Daiichi plant are being evacuated.

[7:40 p.m. ET, 9:40 a.m. Tokyo] Tokyo Electric Power Co. said Sunday that another reactor of its Fukushima nuclear power plants had lost its cooling functions, Kyodo News reports. The utility supplier notified the government Sunday morning that the No. 3 reactor at the No. 1 Fukushima plant had lost the ability to cool the reactor core. The reactor is now in the process of releasing radioactive steam, top government spokesman Yukio Edano said, according to Kyodo News.

It was the sixth reactor overall at the Fukushima No. 1 and No. 2 plants to undergo cooling failure since the massive earthquake and ensuing tsunami struck Japan on Friday.

[6:45 p.m. ET, 8:45 a.m. Tokyo] 15 more people in the vicinity of Fukushima Daiichi's nuclear power plants have been exposed to radioactivity, the Fire and Disaster Management Agency has confirmed, according to Kyodo News.

[6:34 p.m. ET, 8:34 a.m. Tokyo] An aftershock was just felt in Sendai, CNN staff in Japan reports, the latest in a series of aftershocks to rock the quake zone since Friday's 8.9-magnitude earthquake triggered a devastating tsunami.

"People here in Japan are quite used to earthquakes," CNN's Anna Coren said. "The concern is more quakes, more aftershocks could cause more tsunamis. That's what people are worried about."

Since the initial earthquake, there have been 250 aftershocks above 5.0 and almost 50 above 6.0, CNN's Chad Meyers said.

[6:30 p.m. ET, 8:30 a.m. Tokyo] There is currently no evidence of a nuclear meltdown at one of Fukushima Daiichi's nuclear power reactors in northern Japan, Japan's ambassador to the United States said.

"There was a concern about this reactor. We have confirmed that there was a blowup but it was not a blowup of reactor nor container. It was a blowup of the outer building so there was no leakage of the radioactive material," Ichiro Fujisaki told CNN's Wolf Blitzer.

"We are now trying to cope with the situation by putting salt water into the reactor," he said. "There are some other issues with other reactors as well, which need also injection of water or taking out vapor because of increasing pressure into the container and we are now working on it."

When asked if there may be a nuclear meltdown, Fujisaki said, "we do not see any evidence of that at this time."

Engineers have been unable to get close enough to the core to know what's going on, an official with Japan's nuclear and industrial safety agency told CNN Sunday. He based his conclusion on the fact that they measured radioactive cesium and radioactive iodine in the air Saturday night.

[5:48 p.m. ET, 7:48 a.m. Tokyo] A meltdown may be under way at one of Fukushima Daiichi's nuclear power reactors, an official with Japan's nuclear and industrial safety agency told CNN Sunday.

A meltdown is a catastrophic failure of the reactor core, with a potential for widespread radiation release. However, Toshiro Bannai, director of the agency's international affairs office, expressed confidence that efforts to control the crisis would prove successful.

Meanwhile, a second reactor at the same facility failed shortly after 5 a.m. Sunday, the Tokyo Electric Power Company said, according to TV Asahi. The power company said it was having difficulty cooling the reactor and may need to release radioactive steam in order to relieve pressure.

[5:10 p.m. ET, 7:10 a.m. Tokyo] Six canine disaster search teams trained have been deployed to Japan as part of Los Angeles County Task Force 2, Search Dog Foundation said Saturday. The 72-member team was mobilized by USAID and is being sent into the disaster zone along with Virginia Task Force 2. Per USAID, some 75 tons of rescue supplies and equipment for each Task Force are being delivered to the devastated region via military transport. Once on the ground, the job of SDF’s teams will be to comb the wreckage in search of live victims.

[4:57 p.m. ET, 6:57 a.m. Tokyo] Tokyo Disneyland and Tokyo Disney Sea were closed on Saturday to carry out emergency safety checks, Kyodo News reports. The operator said the closure will probably last about 10 days. In Tokyo's Akihabara district, the operator of AKB Theater, a concert hall for exclusive use by all-girl pop idol group AKB48, said the same day the facility will be closed until Tuesday for a similar reason.

[4:48 p.m. ET, 6:48 a.m. Tokyo] The lights were turned off Saturday night at some of the best known landmarks in major Japanese cities after trouble at a Fukushima nuclear plant caused by Friday's massive earthquake prompted calls for electricity savings, Kyodo News reported.

The operator of Tokyo Tower said the move also reflects an intention to express condolences for the victims of the earthquake. Similar decisions were taken with regard to the Tsutenkaku Tower in Osaka, Rainbow Bridge in Tokyo and Bay Bridge in Yokohama, all of which are usually lit up at night, Kyodo reported.

[3:37 p.m. ET, 5:37 a.m. Tokyo] Japanese authorities have informed the International Atomic Energy Agency that the explosion at Unit 1 reactor at the Fukushima Daiichi plant occurred outside the primary containment vessel, not inside, the agency said Saturday. The plant operator, Tokyo Electric Power Company (TEPCO), has confirmed that the integrity of the primary containment vessel remains intact.

As a countermeasure to limit damage to the reactor core, TEPCO proposed that sea water mixed with boron be injected into the primary containment vessel. This measure was approved by Japan's Nuclear and Industrial Safety Agency and the injection procedure began at 8:20 p.m. local Japan time, the agency said. Japan has reported that four workers at Fukushima Daiichi were injured by the explosion, the IAEA said.

[3:17 p.m. ET, 5:17 a.m. Tokyo] The U.S. Nuclear Regulatory Commission has sent two officials with expertise in boiling water nuclear reactors to Japan as part of USAID team.

[2:56 p.m. ET, 4:46 a.m. Tokyo] - There have been no reports of U.S. citizens killed or injured in Japan in the wake of the 8.9-magnitude earthquake and tsunami, according to the U.S. State Department statement. The U.S. State Department will send a consular support team on Sunday into the Sendai area near the earthquake's epicenter, while adding personnel to the U.S. Tokyo embassy in an effort to aid American citizens.

The National Weather Service on Saturday cancelled tsunami advisories for the immediate coastal areas of central and southern California, while warning residents of continued tidal surges in harbors across the region.

[1:20 p.m. ET, 3:20 a.m. Tokyo] Authorities have begun radiation exposure testing around Fukushima prefecture where three people - randomly selected out of a group of 90 - have tested positive for radiation poisoning, according to Japan's government broadcaster, NHK.

[1:14 p.m. ET, 3:14 a.m. Tokyo] Long lines persisted at food stores and at the pump as concern grew in Tokyo that food and fuel shortages may arise in the aftermath of the earthquake.

[1:10 p.m. ET, 3:10 a.m. Tokyo] Gas sales in Tokyo were being limited to 20 liters (5.3 gallons) per car.

[1:04 p.m. ET, 3:04 a.m. Tokyo] Missionaries in Japan serving the U.S.-based Church of Jesus Christ of Latter-day Saints have all been accounted for and are considered safe, the church said Saturday.

[12:27 p.m. ET, 2:27 a.m. Tokyo] Two hundred-fifteen Chinese tour groups visiting Japan have been confirmed as safe, the official Xinhua News Agency reported, citing the country's National Tourism Administration. More than 4,500 Chinese tourists were in Japan at the time of the quake and tsunami, the agency reported.

[11:49 a.m. ET, 1:49 a.m. Tokyo] Japan public broadcaster NHK reported the country's Defense Ministry had sent a unit that specializes in dealing with radioactive contamination to a command post near the stricken plant.

[11:48 a.m. ET, 1:48 a.m. Tokyo] The British government will dispatch a team of 59 fire service search and rescue specialists, two rescue dogs and a medical support team to join the international relief effort in Japan.  They will take up to 11 tons of specialist rescue equipment, including heavy lifting and cutting equipment to save the lives of people who are trapped in the debris.

[10:51 a.m. ET, 12:51 a.m. Tokyo] About 50,000 Japan Self-Defense Force personnel were being deployed Saturday in quake and tsunami relief efforts, according to a Kyodo report in The Japan Times. Japan's Defense Ministry said 190 aircraft and 25 ships were involved in the effort, according to the report.

[10:23 a.m. ET, 12:23 a.m. Tokyo] In Shiroishi, a town near the area hardest hit by the quake, two SH-60 helicopters from U.S. Naval Air Facility Atsugi delivered 1,500 pounds of rice and bread donated by people in Ebina, southeast of Tokyo, the U.S. 7th Fleet, said in a statement Saturday.

[10:03 a.m. ET, 12:03 a.m. Tokyo] Japan's government has ordered the evacuation of residents within 20 kilometers of one nuclear power plant and within 10 kilometers of a second. More than 83,000 people live within 10 kilometers of the two plants, according to Japan's Nuclear and Industrial Safety Agency.

[9:48 a.m. ET, 11:48 p.m. Tokyo] Tokyo Electric Power Company warned Saturday that many areas could experience blackouts as quake and tsunami damage has forced power plants to shut down and put a strain on electrical supplies, the Japan Times reported. As of noon Saturday Japan time, 5.1 million households were without power, according to the report.

[9:04 a.m. ET, 11:04 p.m. Tokyo] An estimated 6.4-magnitude earthquake has hit near the east coast of Honshu - the latest in a series of aftershocks striking on and around Japan's largest island in the past 24 hours. The aftershock occurred at 10:15 p.m. and just 82 kilometers (about 50 miles) from Fukushima, where officials are assessing a nuclear reactor damaged by Friday's earthquake and tsunami.

[8:49 a.m. ET, 10:49 p.m. Tokyo] The walls of a concrete building surrounding the reactor container at the Fukushima Daiichi nuclear plant collapsed in an explosion, but the reactor and its containment system were not damaged, Chief Cabinet Secretary Yukio Edano said.

[8:37 a.m. ET, 10:37 p.m. Tokyo] About 9,500 people are unaccounted for in the town of Minamisanriku in Miyagi prefecture , officials said Saturday, according to Kyodo News Service. The figure is more than half of the population of 17,000 in the town on the Pacific coast, they said.

[8:35 a.m. ET, 10:35 p.m. Tokyo] Japanese authorities are making plans to distribute stable iodine, a treatment to prevent radiation poisoning, to residents near two damaged nuclear plants, the International Atomic Energy Agency says.

[8:03 a.m. ET, 10:03 p.m. Tokyo] An explosion at an earthquake-damaged nuclear plant was not caused by damage to the nuclear reactor but by a pumping system that failed as crews tried to bring the reactor's temperature down, Chief Cabinet Secretary Yukio Edano said Saturday.

The next step for workers at the Fukushima Daiichi plant will be to flood the reactor containment structure with sea water to bring the reactor's temperature down to safe levels, he said.  The effort is expected to take two days.

Radiation levels have fallen since the explosion and there is no immediate danger, Edano said.

[8:01 a.m. ET, 10:01 p.m. Tokyo] U.S. Marine Corps cargo aircraft and helicopters were being dispatched from bases on the southern Japanese island of Okinawa to mainland Japan to help in quake and tsunami relief efforts, the III Marine Expeditionary Force said in a statement.

[7:54 a.m. ET, 9:54 p.m. Tokyo] Japanese Prime Minister Naoto Kan called the natural disaster that struck his country Friday "unprecedented" and said the quake caused a bigger tsunami than expected. Kan said that "we'd first like to focus on saving lives and secondly the comfort of the evacuees" and "there will be many resources that will be needed for this evacuation process."

[7:24 a.m. ET, 9:24 p.m. Tokyo] Dozens of aftershocks from Friday's 8.9-magnitude earthquake jolted Japan on Saturday. Four of Saturday's temblors were of magnitude 6.0 or above, according to the U.S. Geological Survey.

[7:07 a.m. ET, 9:07 p.m. Tokyo] Fires were burning at more than 200 locations in 12 prefectures after Friday's earthquake and tsunami, Japanese broadcaster NHK reported, citing the nation's Fire and Disaster Management Agency.

[6:54 a.m. ET, 8:54 p.m. Tokyo] The explosion at Japan's Fukushima nuclear plant was not caused by the nuclear reactor but by "water vapor that was part of the cooling process," Chief Cabinet Secretary Yukio Edano said Saturday. He said no harmful gases had been emitted by the explosion.

[6:44 a.m. ET, 8:44 p.m. Tokyo] Japanese Prime Minister Naoto Kan confirms that the evacuation area around the Fukushima Daiichi nuclear plant has been increased to 20 kilometers. But no one has been harmed by radiation, he says.

[6:23 a.m. ET, 8:23 p.m. Tokyo] No people were visible Saturday in the streets of Minamisoma, Japan, a city whose population on Friday had been 70,000. All that was left of many structures were their foundations. Only concrete and steel buildings appeared to have withstood the wash.

[6:18 a.m. ET, 8:18 p.m. Tokyo] Authorities extended the evacuation area around the Fukushima Daiichi nuclear plant to 20 kilometers, Kyodo News Agency reported.

[6:11 a.m. ET, 8:11 p.m. Tokyo] The roof of a reactor at Japan's Fukushima nuclear plant collapsed following an explosion around 3:30 p.m. (1:30 a.m. ET), Japan's Kyodo News Agency reported, citing Tokyo Electric Power Company.

[5:59 a.m. ET, 7:59 p.m. Tokyo] The powerful earthquake that unleashed a devastating tsunami Friday appears to have moved the main island of Japan by 8 feet (2.4 meters) and shifted the Earth on its axis, a U.S. Geological Survey geophysicist reports.

[5:17 a.m. ET, 7:17 p.m. Tokyo] Friday's earthquake and tsunami crippled cooling systems at two Japanese nuclear power plants and workers were working Saturday to contain temperatures.

"This is a situation that has the potential for a nuclear catastrophe. It's basically a race against time, because what has happened is that plant operators have not been able to cool down the core of at least two reactors," said Robert Alvarez, a senior scholar at the Institute for Policy Studies in Washington.

[4:47 a.m. ET, 6:47 p.m. Tokyo] At least seven homes sustained substantial tsunami damage on Hawaii's Big Island, including one that was pulled into a bay. Hotels in Kailua-Kona also reported damage. CNN affiliate KHON has a full report.

[4:22 a.m. ET, 6:22  p.m. Tokyo] The Tokyo Electric Company said four workers were injured in an explosion at the Fukushima Daiichi plant. NHK said the injured workers were in the process of cooling a nuclear reactor at the plant by injecting water into its core.

[3:46 a.m. ET, 5:46  p.m. Tokyo] Rescuers plucked dazed survivors from collapsed homes, muddy waters and raging fires Saturday, a day after a powerful earthquake tore through Japan and unleashed waves that swallowed entire towns along the coast.

More than 900 were killed and about 700 others were missing Japanese public broadcaster NHK reported. The number is expected to go up as rescuers reach more hard-hit areas.

The  8.9-magnitude quake was centered about 130 kilometers (80 miles) from Sendai, a farming and fishing region battling to stay ahead following decades of brain drain from its youth moving to  the capital of Tokyo.

[3:08 a.m. ET, 5:08  p.m. Tokyo] An explosion has been reported near a nuclear plant in northeastern Japan's Fukushima prefecture, Japanese public broadcaster NHK reported, citing the country's nuclear and industrial safety agency.

[2:19 a.m. ET, 4:19  p.m. Tokyo] A small amount of  radioactive Cesium has escaped into the air surrounding a nuclear plant in northeastern Japan's Fukushima prefecture, Japan's Nuclear and Industrial Agency said.

The agency said there was a strong possibility that this was caused by the melting of a  fuel rod, adding that plant engineers were continuing to cool the fuel rods by  pumping water around the rods.

[2:17 a.m. ET, 4:17  p.m. Tokyo] Japanese public broadcaster NHK reported Saturday that the death toll after an 8.9-magnitude earthquake and tsunami is more than 900, with about 700 others reported missing.

Earlier Saturday the nation's Kyodo News News Agency, citing police, reported that the death toll was 433, with at least 784 missing.

The official death toll is likely to rise as authorities continue rescue and relief efforts in the worst-hit areas.

[2:00 a.m. ET, 9:00 p.m. Hawaii] Hawaii Governor Neil Abercrombie signed a "State of Disaster  Proclamation" after the tsunami caused millions of dollars or damages as it swept through the islands. The proclamation will allow Hawaii to get federal funds to help rebuild, the governor said in a statement.

[12:00 a.m. ET, 2:00 p.m. Tokyo] The death toll from the 8.9-magnitude earthquake that hit Japan rose to 433, the nation's Kyodo News reported Saturday. At least 784 are missing, Kyodo said, citing police.

[11:01 p.m. ET, 1:01 p.m. Tokyo] At least 398 people are dead and 805 are missing after the massive earthquake in Japan, the Kyodo News Agency reported Saturday. Earlier, the news agency said the death toll from the massive earthquake would likely surpass 1,000.

[10:01 p.m. ET, 12:01 p.m. Tokyo] As rescue crews continue to account for the damage caused by the country's largest earthquake on record, people in Japan on Saturday are struggling to contact loved ones near the hardest hit areas.

Lucy Craft, a freelance correspondent in Tokyo, has a teenage son at a high school near the epicenter in Sendai, northeast of Tokyo. More than 18 hours after the quake, she hadn't been able to make contact.

"The phone lines are still down... I haven't been able to get in touch with him by cell phone, I haven't been able to contact anybody there. I have his teacher's phone number," Craft said Saturday morning in Tokyo. "It's a very upsetting situation, as you can imagine."

[10:32 p.m. ET, 12:32 p.m. Tokyo] Residents of northern Japan streamed south from their earthquake-stricken hometowns Saturday, crowding stores in search of vital supplies as rescue teams worked north toward the historic quake's epicenter.

Roads and buildings showed cracks as far away as 200 kilometers (125 miles) from Sendai, the closest city to the epicenter. One man told CNN the scene in towns hit by the quake and the resulting tsunami was "unimaginable."

Shoppers were polite but tense as they sought food, water and gasoline from stores where shelves were quickly emptied and pumps soon ran dry.