WASHINGTON (AP) - A person briefed on the Boston Marathon investigation says the explosives were in 6-liter pressure cookers and placed in black duffel bags.
The person says the explosives were placed on the ground and contained shards of metal, nails and ball bearings. The person spoke on the condition of anonymity because the investigation was ongoing.
The person says law enforcement officials have some of the bomb components but did not yet know what was used to set off the explosives.
President Barack Obama said Tuesday the bombings were an act of terrorism but investigators do not know if they were carried out by an international or domestic organization, or perhaps by a "malevolent individual."
Three people were killed, including an 8-year-old boy, by two explosions just seconds apart near the finish line.
Police commissioner Ed Davis says 176 victims came to hospitals around Boston, and 17 of those are in critical condition.
Special Agent in Charge Richard DesLauriers says at a news conference there are no known additional threats.
Police commissioner Ed Davis says it is the most complex crime scene in history of the department.
Authorities are looking for amateur video and photographic evidence that can give clues to who set off the bombs.
Suffolk County District Attorney Daniel Conley says "what occurred in Boston was an act of cowardice."
BOSTON (AP) - The young victim of the Boston Marathon bombings is being remembered as a vivacious boy who loved to run and climb.
Eight-year-old Martin Richard was among the three people killed in the explosions. That's according to a person who spoke with a friend of the family.
A candle burned on the stoop of the family's single-family home in the city's Dorchester section today, and the word "Peace" was written in chalk on the front walkway.