[Update at 10:25 p.m.] Two suspicious packages found abroad that were bound for Jewish organizations in the United States contained a massive amount of explosive material that would have triggered a powerful blast had the suspected terror plot not been thwarted, a source close to the investigation said Friday.

[Update at 9:55 p.m.] A Yemeni diplomat in Washington says the Yemeni government has opened a full scale investigation into a suspicious device that was shipped from the country to the East Midlands Airport in the United Kingdom.

President Obama's counterterrorism adviser, John Brennan, has been in discussions with Yemen President Ali Abdullah Saleh about how to address the threat, a senior U.S. official said.

Yemen Embassy spokesman Mohammed Albasha in Washington said no UPS or FedEx flights take off or land in Yemen.

"It is way too early to rush to conclusions," Albasha said. "We have had heightened security at our airport(s) and have been working very closely on
security with our regional partners including the U.K. and U.S. since the Christmas incident" involving the accused would-be bomber now known as the "Underwear Bomber." 

Meanwhile, British police sources said the discovery of the suspicious package at East Midlands Airport was the result of an intelligence tip rather than a random check.

[Update 8:54 p.m.] Synagogues across metropolitan Chicago, Illinois, began taking "appropriate precautions" Friday after officials warned them to watch out for suspicious packages from abroad, a Jewish Federation spokeswoman said.

President Obama said two packages that apparently contained explosive materials were bound for two synagogues in Chicago.

While there were "no identifiable or specific threats," an FBI official in Chicago said suspicious packages addressed to U.S. destinations found on cargo planes abroad warranted the precautions.

Read the full story on CNN.com.

[Update 8:20 p.m.] The Emirates flight that was escorted into JFK International Airport this afternoon has been cleared, FBI Special Agent Richard Kolko said. Officials originally flagged flight 201 because there was cargo from Yemen aboard.

Read more on CNN.com.

[Update 8:00 p.m.] A U.S. official said it is likely that the material used in two suspicious packages bound for the United States was PETN - a highly explosive organic compound belonging to the same chemical family as nitroglycerin - but testing continues to reach a definitive conclusion.

PETN was allegedly one of the components of the bomb concealed by Umar Farouk AbdulMutallab, who is accused of trying to set off an explosion aboard Northwest Airlines Flight 253 as it approached Detroit, Michigan, on December 25. Al Qaeda in the Arabian Peninsula is also believed to be behind that botched attack.

Declining to provide specifics, White House counterterrorism chief John Brennan said intelligence officials were specifically looking for such suspicious packages when the first package was found in the United Kingdom.

He later issued a statement thanking Saudi Arabia, saying the United
States is "grateful" for the country's help in identifying the threat.

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