BOSTON (AP) -- The FBI is confirming that pressure cookers may have been used in the Boston Marathon bombings that killed three and wounded more than 170.
FBI special agent in charge Richard DesLauriers spoke at a news conference Tuesday.
[SPECIAL COVERAGE: BOSTON MARATHON TERROR ATTACK
He says pieces of black nylon and fragments of ball bearings and nails were found and authorities believe the bombs were placed in a dark-colored backpack or bag.
A source close to the investigation had said earlier that the bombs were made in 1.6-gallon pressure cookers, one containing shards of metal and ball bearings, the other packed with nails, and both stuffed into duffel bags.
A second person briefed on the investigation confirms that at least one of the explosives was made of a pressure cooker. Both spoke on condition of anonymity because the investigation is ongoing.