WASHINGTON (Bloomberg)—President Barack Obama said two packages shipped from Yemen and directed to Jewish institutions in Chicago contained explosive materials and were intercepted.

The discovery, in the U.K. and Dubai, triggered an examination of air cargo flights in the U.S.

“The American people should know that the counterterrorism professionals are taking this threat very seriously and are taking all necessary and prudent steps to ensure our security,” President Obama, who was notified of the threat last night, said in remarks at the White House.

President Obama said examination of the packages showed they contained explosive material, leading the president and his top intelligence aides to conclude there is “a credible terrorist threat against our country.”

He said the U.S. is pursuing the investigations and pledged to “destroy this al-Qaeda affiliate” based in Yemen.

Authorities are investigating whether the shipments were staged as rehearsals for a future attack, a U.S. official said.

President Obama’s homeland security and counterterrorism adviser, John Brennan, said the devices were “intended to do harm.”

The U.S. is giving greater scrutiny to packages from Yemen as a result, Mr. Brennan said.

The Federal Bureau of Investigation checked packages on three United Parcel Service Inc. jets from Europe. Two of the planes landed in Philadelphia and another in Newark, N.J., UPS spokesman Mike Mangeot said Friday. The Newark jet was later cleared for another flight.

Mr. Brennan notified Obama at 10:35 p.m. Thursday and the administration coordinated a response with federal agencies including the Central Intelligence Agency, Homeland Security and the Federal Aviation Administration, White House press secretary Robert Gibbs said after President Obama spoke.

The alert on the planes comes on the heels of the arrest of a Virginia man whom Justice Department prosecutors say participated in what he thought was an al-Qaeda plot to bomb subway stations in the Washington area. Farooque Ahmed, 34, of Ashburn, a U.S. citizen born in Pakistan, is being held without bail.

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White House statement

“Based on close cooperation among U.S. government agencies and with our foreign allies and partners, authorities were able to identify and examine two suspicious packages, one in East Midlands, United Kingdom, and one in Dubai,” the White House said. “Both of these packages originated from Yemen.”

Maury Lane, a spokesman for Memphis, Tenn.-based FedEx, said he didn't have additional information about the shipper or contents of the package in Dubai. The government media office in Dubai declined to comment.

All three UPS planes landed safely in the U.S., with two in Philadelphia and one in Newark, N.J., UPS spokesman Mike Mangeot said Friday in a telephone interview. The Newark jet was later cleared for another flight, he said.

“Out of an abundance of caution, the planes were moved to a remote location where they are being met by law enforcement officials and swept,” the Transportation Security Administration said in a statement.

UPS' Mr. Mangeot said the FBI and TSA haven't given UPS further details about the nature of the packages or what is under investigation. He said he wasn't aware of any visible signs of smoke or fire from the packages or on the Atlanta-based company's planes.

UPS planes

A Boeing Co. 767 from Paris and an MD-11 from Cologne, Germany, landed in Philadelphia, and a 767 flew to Newark from East Midlands, Mr. Mangeot said. He said the Newark jet was now on another flight, to Louisville, Ky.

A UPS truck that had been stopped in Brooklyn for a suspected explosive device was cleared following an investigation, said Paul Browne, a spokesman for the New York City Police Department, in an e-mail.

A person at UPS' office in Sana'a, the Yemeni capital, said the manager was unavailable, refused to comment further and declined to give his name, saying he wasn't authorized to comment.

The Jewish Federation of Metropolitan Chicago, a not-for- profit charity group, was advising local synagogues to take “appropriate precautions” Friday after being notified by authorities to be on alert, said Linda Haase, a spokeswoman for the group, in a telephone interview.

The U.S. got a tip from one its allies about packages coming from Yemen destined for synagogues in Chicago, CNN reported, citing an unidentified person in law enforcement.

Copyright 2010 Bloomberg