WASHINGTON (AP) -- U.S. officials say al-Qaida's sophisticated new underwear bomb contained a chemical that was also used in a failed 2010 effort to take down U.S.-bound cargo planes.
The cargo plot failed, but only because the United States was tipped off to the bombs. The bombs made it past cargo handlers and airport screeners.
In those bombs, the detonator was lead azide. Officials say the same chemical was used inside this latest bomb recovered by the CIA.
That could explain why officials describe this new bomb as an upgrade over the Christmas 2009 underwear bomb. That bomb did not use lead azide as a detonator and it failed to ignite aboard a plane over Detroit.
The officials spoke on condition of anonymity because they were not authorized to discuss the information publicly.