On board the Costa Concordia, thousands of passengers were dining, drinking, attending a magic show, perhaps trying their luck in the casino.

It was Friday night on the luxury cruise liner, sailing in the Mediterranean off the Italian coast with about 3,200 passengers and 1,000 crew members - a night of entertainment and relaxation.

There was annoyance, but no real alarm, when the lights went out - not at first. Passenger Vivian Shafer said she thought it was part of the magic show.

Then, a magical night turned into a nightmare.

Those on board then heard an ominous scraping sound, and the 951-foot vessel gave a shudder. The ship began to list to one side.

Photos: See high-resolution images of the ship

The ship was carrying about 3,200 passengers and 1,000 crew members when it ran aground Friday night.

5 facts about the Costa Concordia cruise ship

Now, rescue efforts continue as the ship's operator and prosecutors try to figure out exactly what happen and who is to blame.

Rescue efforts continue

After a brief suspension, rescue efforts resumed Monday on the partially sunken cruise liner Costa Concordia, officials said.

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The ship struck rocks Friday night and rolled onto its side, leaving at least six people dead.

The search was suspended earlier Monday because the vessel began to move, said Sergio Ortelli, mayor of the nearby island of Giglio.

Coast Guard spokesman Filippo Marino said efforts had resumed, adding that rescuers will focus on retrieving the body of a man, presumably a passenger, discovered earlier in the day. However, he said the forecast has rescuers worried, as it calls for rising winds. The head of the company that owns the ship said Monday he has not given up hope of finding survivors.

"Hope is the last thing to die," said Costa Cruises chairman and chief executive Pier Luigi Foschi. About 16 people remained unaccounted for as of Monday following the collision off the Italian coast on Friday evening.

Rescuers brave cold, darkness to scour listing cruise ship

By all accounts, things went bad the moment the ship struck rocks Friday night and rolled onto its side.

But what led up to that moment?

Why was the ship  so close in to shore in an area where local sailors say the sea bed is pockmarked with rocks? What happened in the minutes after the ship ran aground? Why was no "mayday" distress signal sent?

Costa Cruises issued a statement saying "preliminary indications are that there may have been significant human error on the part of the ship's master, Captain Francesco Schettino."

"The route of the vessel appears to have been too close to the shore, and the captain's judgment in handling the emergency appears to have not followed standard Costa procedures," the statement added.

Costa Cruises chairman and chief executive Pier Luigi Foschi placed blame for the wreck squarely on the captain, however, saying Schettino had deviated from frequently traveled routes.

"The captain decided to change the route and he went into water that he did not know in advance," Foschi said. He said the company was limited in its ability to investigate the incident because they did not have the data recorder.

Italian prosecutors Monday ruled out a technical error as the cause of the incident, saying the captain was on the bridge at the time and had made a "grave error."

Captain Francesco Schettino is under arrest and may face charges including manslaughter, shipwreck, and abandoning a ship when passengers were still on board, Italian prosecutor Francesco Verusio said.

Schettino denies the assertion that he had steered the ship too far inland.

"We were about 300 meters (1,000 feet) from the shore, more or less," Schettino said after the accident.

There was a "lateral rock projection," he said.

"Even though we were sailing along the coast with the tourist navigation system, I firmly believe that the rocks were not detected, as the ship was not heading forward but sideways, as if underwater there was this rock projection," he said.

Environmental concerns

Environmental campaign group Greenpeace has warned that if oil leaks from the stricken cruise liner  it could cause an environmental disaster, threatening marine life including birds, whales and sharks.

The vessel - containing hundreds of tons of fuel oil - is now partially submerged off the Italian island of Giglio, which lies inside the Pelagos Sanctuary for Mediterranean Marine Mammals.

The sanctuary was set up 10 years ago in an agreement between France, Italy and Monaco, with about half of it existing in international waters. Pelagos is a haven for many marine species including the fin whale, sperm whale, bottlenose dolphin, tuna, swordfish and sharks, as well as supporting sea bird populations.

Costa chairman and chief executive Foschi confirmed that the vessel is carrying 2,300 tons of oil, split between heavy fuel oil and gas oil.

"It is in a sea we want to protect," he said. "We are taking steps to avoid environmental issues."

In a statement, Costa Cruises said: "We have engaged the services of a worldwide leader, a specialized salvage company to develop an action plan and help establish a protection perimeter around the ship."

Greenpeace is concerned that other toxic substance that may be on board - such as lubricants and paints - could spill into the sea and get into the food chain.