adminSurgeons at several Boston hospitals told televised news conferences on Tuesday that the explosive devices had apparently been packed with small pellets and sharp “nail-like” objects that were designed to maim their victims.
The new details about the explosives emerged as President Obama announced at the White House that the F.B.I. was investigating the attack as “an act of terrorism,” but said that it was unclear if it had been carried out by an individual or a group, foreign or domestic.
Representative Michael McCaul, a Texas Republican who heads the House Homeland Security Committee, said the authorities believe that the explosives were similar to improvised explosive devices that have been used against American troops in Iraq and Afghanistan.
Mr McCaul, a former federal prosecutor who received briefings Tuesday morning from Federal Bureau of Investigation and Homeland Security officials, also said that the authorities still did not know whether the attack was a foreign or domestic plot.
A law enforcement official said at least one and probably both of the bombs were pressure cookers filled with nails and ball bearings and black powder that were detonated with rudimentary “kitchen-type” timers. The official said investigators believe the bombs were hidden inside bags or backpacks and left on the street or sidewalk near the finish line.
A senior government official who had spoken with intelligence and law enforcement officials said Tuesday that there had been “no pre-attack chatter” detected by the government from members of Al Qaeda or other terrorist groups. In two intelligence briefings the official said he had received in recent weeks, “nothing was offered on this” type of attack.
The official said that the intelligence agencies had begun to go back and examine communications they intercepted in recent weeks to determine whether they had missed anything.
“Before the 2009 Christmas Day bombing attempt, they thought there was no pre-attack chatter,” said the official. “But there had been, but it had not been interpreted. Everything is now being looked at.”
Along with having few investigative leads, the official said that the investigation had been hampered, in part, by the fact that no terrorist group had claimed responsibility for the attack. Such a claim of responsibility, the official said, would help investigators as they try and weed out suspects. — New York Times
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