By CBS News chief investigative correspondent Armen Keteyian and investigative producer Pat Milton.
British Intelligence has confirmed perhaps the most chilling boast that accused Christmas Day bomber Umar Abdulmutallab made to investigators after his arrest: that close to 20 other young Muslim men were being prepared in Yemen to use the same technique to blow up airliners, CBS News chief investigative correspondent Armen Keteyian reports exclusively.
"I think the fact we know that there are other operatives being trained by al Qaeda in Yemen is extremely troubling, and is the most dangerous dimension to come out of the December 25th event," said CBS News national security analyst Juan Zarate.
That is why, sources say, the U.S. government issued this directive last Sunday - announcing "enhanced screening" for "every individual" onfrom 14 countries, including Afghanistan, Somalia and Yemen.
In addition, a team of, having arrived last Saturday, attempting to piece together Abdulmutallab's whereabouts and activities in the two weeks prior to the attempted attack on Flight 253.
According to a government official, Abdulmutallab first arrived in the Ghana capitol of Addis Ababa on December 9 after spending five months in Yemen.
U.S officials strongly suspect Abdulmutallab met Al Qaeda operatives in Ghana who may well have offered final preparations for his suicide mission investigating if it was there that the would-be bomber obtained the specially-designed underwear packed with highly explosive powder.
"One of the keys is to get to London, to Ghana, to Nigeria, to Yemen to find out who Abdulmutalab was talking to, what he was doing, what else may be at play here with respect to a pipeline coming out of Yemen to hit the United States," Zarate said.