Feds Dissect Boston Marathon Bombs

April 23, 2013 — -- Federal agents have analyzed the two pressure cooker bombs used in the Boston Marathon attack and confirmed early speculation that they were built largely, if not entirely of commercially available items, including parts of a remote control toy car, BBs and small nails.

The analysis was circulated to law enforcement agencies Tuesday evening in a federal law enforcement joint intelligence bulletin. Analysts dissected the remnants of the bombs and determined that they were packed with low grade explosives, fragmentation materials such as nails and BBs, and an electrical fusing systems cannibalized from the remote control car.

FULL COVERAGE: Boston Marathon Bombing

The report notes that a similar device was found in the thwarted 2010 attempt to set off explosives in Times Square.

"Terrorists can exploit the innocuous appearance and transportability of pressure cookers to conceal IED components," the bulletin says.

The bulletin says the exact type of explosives used are not known. But earlier Tuesday, ABC News affiliate WMUR reported that Tamerlan Tsarnaev bought two large pyrotechnic devices in February from a New Hampshire branch of a national fireworks chain. A similar report in The New York Times said executives at the chain's parent company discovered the purchase in their records and reported it to authorities.

The charging document filed in the case against 19-year-old Dzhokhar Tsarnaev also notes that FBI agents found "a large pyrotechnic" in his college dorm room.

A federal law-enforcement official briefed on the probe told ABC News that investigators remain unsure if the explosives used to kill three and injure 250 were built from fireworks or other sources.