President Obama said Friday that two suspicious U.S.-bound packages sent from Yemen and intercepted in Dubai and Britain's East Midlands airport apparently contained explosive material, posing a "credible terrorist threat against our country."
"An initial examination of those packages has determined that they do apparently contain explosive material," Obama said.
The president also said White House counterterrorism adviser John Brennan spoke to Yemeni President Ali Abdullah Saleh, who had assured the U.S. of the full cooperation of his government.
Brennan told reporters an initial analysis suggested that the explosives "were in a form that was designed to try to carry out some type of attack."
Earlier, White House spokesman Robert Gibbs said the searches of the planes in Dubai and in East Midlands on Thursday night triggered Friday's searches on cargo flights at airports in Philadelphia and New Jersey.
"The president directed U.S. intelligence and law enforcement agencies, and the Department of Homeland Security, to take steps to ensure the safety and security of the American people, and to determine whether these threats are a part of any additional terrorist plotting," the White House said in a statement.
Yemen is home to the al-Qaida branch that tried to bomb a Detroit-bound airliner on Christmas.
In addition, U.S. fighter planes escorted a passenger plane from Dubai as it approached New York's John F. Kennedy Airport on Friday. An FBI spokesman said there was no known threat related to the flight.
Obama was notified of a potential terrorist threat at 10:35 p.m. ET Thursday by Brennan, Gibbs said in a statement.
The Department of Homeland Security said Friday that travelers should expect to see heightened cargo screening and additional security at airports.
Authorities confirmed that two of the planes searched Friday landed at Philadelphia International Airport — one coming in from Paris and another from Cologne, Germany. Both were taken to a remote tarmac for inspection. The third flight originated in East Midlands, and the FBI was inspecting that plane at New Jersey's Newark Liberty Airport.
The suspicious package in Dubai was found at a FedEx facility and confiscated by local authorities, according to FedEx spokesman Maury Lane. He said FedEx has placed an indefinite embargo on all shipments originating from Yemen and is cooperating fully with law enforcement.
Authorities also told NPR that a UPS truck in the New York City borough of Brooklyn was swept because of a suspicious package. The New York Police Department and the FBI could not provide details on that incident.
Reports of suspicious packages are common. But Friday's events were unusual because of the sheer number and the various cities that were simultaneously involved. Law enforcement officials said the checks were being done "out of an abundance of caution."
NPR's Dina Temple-Raston, Carrie Johnson and Scott Horsley contributed to this report, which also contains material from The Associated Press
