By JAY LINDSAY and EILEEN SULLIVAN FBI agents gather near the finish line of the Boston Marathon in Boston Tuesday, April 16, 2013. The bombs that ripped through the crowd at the Boston Marathon, killing at least three people and wounding more than 170, were fashioned out of pressure cookers and packed with shards of metal, nails and ball bearings to inflict maximum carnage, a person briefed on the investigation said Tuesday. (AP Photo/Winslow Townson) 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. 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.