The FBI's Chicago office said that the packages "in question" had been addressed to two Chicago locations, but would not provide further details. The FBI "notified the targeted institutions" by phone this morning, according to a spokesman. The White House said that the synagogue across the street from the president's home in Chicago was not one of the synagogues targeted.
The Anti-Defamation League released a statement that said it had learned from "law enforcement sources" of a reported threat to Jewish institutions in packages shipped from the U.K., Yemen and Saudi Arabia, and that it had sent notice to Jewish organizations across the U.S.
While President Obama did not say that Al Qaeda in the Arabian Peninsula was behind the apparent bombing attempt, he did note Friday that Al Qaeda's Yemeni offshoot continues to seek ways to attack the United States.
The radical American-born cleric Anwar a-Awlaki has repeatedly called on for attacks on the U.S. from his base in Yemen.
American officials believe that AQAP has trained hundreds of terrorists whose prime objective is to attack the US, including the so-called underwear bomber Umar Farouk Abdulmutallab.
"Yemen is the home of between 500 and 600 al Qaeda fighters, three or four times the number of al Qaeda fighters in Afghanistan," said Richard Clarke, former White House counterterrorism official and now an ABC News consultant. "This is really a place where Al Qaeda is operating, where it's strong, where it has training camps, where we know they have trained people and sent them to the United States."
U.S. authorities have now ordered every package shipped from Yemen to the U.S. to be inspected.
FedEx also said in a statement that local authorities, in cooperation with the FBI, had "confiscated a suspicious package at the FedEx facility in Dubai. The shipment originated in Yemen and as an additional safety measure, FedEx has embargoed all shipments originating from Yemen."
The method of trying to ship the improvised explosives into the country on air cargo flights exposed one of the worst-kept secrets about American security.
At best, only a third of packages coming into the country as air cargo are ever inspected.
"I've called cargo the soft underbelly of aviation security because of the relative little security that is attached to it," said Clark Kent Ervin, former inspector general of the Department of Homeland Security. "I think this just underscores that fact that al Qaeda is always probing for weaknesses in the system and when we close one vulnerability, al Qaeda is just going to find another."
On Friday, Homeland Security agents and intelligence analysts were ordered to go back through previous shipments from Yemen over the last two weeks, as the White House worried that other package bombs might have already made their way into the country.