Two packages containing explosives, shipped from Yemen and addressed to synagogues in Chicago, were intercepted in Britain and Dubai, setting off a broad terrorism scare on Friday that included the scrambling of fighter jets to accompany a passenger flight as it landed safely in New York.
The discovery of the explosives packed in toner cartridges for computer printers, based on a tip from Saudi intelligence officials, began an urgent hunt for other suspicious packages in the United States and other countries.
Cargo planes were moved to secure areas of airports in Philadelphia and Newark for searches, and a United Parcel Service truck in Brooklyn was stopped and inspected. No additional explosives had been discovered by late Friday.
Representative Jane Harman, a California Democrat on the House Homeland Security Committee, said Friday that the packages seized in Britain and Dubai contained PETN, the same chemical explosive contained in the bomb sewn into the underwear of the Nigerian man who tried to blow up an airliner over Detroit last Dec 25. That plot, too, was hatched in Yemen, a country that is regarded as one of the most significant fronts in the battle with extremists.
Ms. Harman, who was briefed by John S Pistole, administrator of the Transportation Security Administration, said that both packages contained computer printer cartridges filled with the explosive, but that one used a cell phone as a detonator and the other had a timer.
In a brief statement to reporters at the White House on Friday afternoon, President Obama, who had been briefed on developments starting at 10:35 pm on Thursday, said the explosives represented a "credible terrorist threat" to the United States.
"The events of the past 24 hours underscore the necessity of remaining vigilant against terrorism," Obama said. He praised the work of intelligence and counterterrorism officials in foiling the plot. "The American people should be confident that we will not waver in our resolve to defeat al-Qaeda and its affiliates and to root out violent extremism in all its forms," the president said.
News of the terrorist plot came as Obama was barrelling into the last four days of campaigning before midterm elections on Tuesday, and White House officials appeared determined to project the appearance of a commander in chief who was on top of the developments.