Investigators painstakingly gathering fragments of evidence from the two explosions that killed 3 people at the Boston Marathon have recovered the lid from a pressure cooker apparently used as the explosive device, according to a federal law enforcement source.
The official, who has been briefed on the matter but is not authorized to comment publicly, told USA TODAY the lid was found on a roof near the scene of the blast.
ATF spokesman Special Agent Steven Bartholomew, who would not comment on the report of the lid, did say that the location of debris on rooftops indicates the great force of the blast.
He said authorities will measure the distances and examine other evidence in the blast radius to determine where the bomb was located when it exploded.
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