WASHINGTON -- U.S. airlines have been warned by the federal Department of Homeland Security about credible threats that shoe bombs may be used to attack commercial passenger jets, an agency official said.
The department told airport screeners to check passengers' shoes for traces of explosives, said the official, who wasn't authorized to talk publicly about a continuing investigation. There was no indication of a specific bomb plot, according to the official.
Homeland Security's alert followed the U.S. government's Feb. 6 ban on all liquids, gels and aerosols from carry-on luggage on flights to Russia shortly before the start of the Winter Olympics.
The restrictions were triggered by warnings that terrorists might hide bomb-making materials in toothpaste tubes for assembly into an explosive device during or after flights.
"Out of an abundance of caution, DHS regularly shares relevant information with domestic and international partners about relevant threat information," Homeland Security said Wednesday in a statement. "These types of regular communications are part of that important priority."
Onboard explosives have been a focus for U.S. aviation security in the years since the Sept. 11, 2001, terror attacks.
Umar Farouk Abdulmutallab was sentenced to life in prison in 2012 after he was convicted of attempting to bomb a Delta Air Lines Inc. jet approaching Detroit with explosives hidden in his underwear on Christmas Day 2009.
In 2002, Richard C. Reid pleaded guilty to trying to blow up an American Airlines jet over the Atlantic on Dec. 22, 2001, with explosives in his high-top sneakers. Authorities said the explosives were powerful enough to rip a hole in the aircraft's fuselage.
That incident led to the Transportation Security Administration procedure requiring passengers to remove their shoes for screening while going through security checkpoints.