— BOSTON (AP) — The bombs that ripped through the Boston Marathon crowd appear to have been fashioned out of ordinary kitchen pressure cookers, packed with nails and other fiendishly lethal shrapnel, and hidden in duffel bags left on the ground, investigators and others close to the case said Tuesday.
President Barack Obama branded the attack an act of terrorism, whether carried out by a solo bomber or group, and the FBI vowed to "go to the ends of the Earth" to find out who did it.
Scores of victims remained in Boston hospitals, many with grievous injuries, a day after the twin explosions near the marathon's finish line killed three people, wounded more than 170 and reawakened fears of terrorism. A 9-year-old girl and 10-year-old boy were among 17 victims listed in critical condition.
Officials found that the bombs consisted of explosives put in common 1.6-gallon pressure cookers, one containing shards of metal and ball bearings, the other packed with nails, and both stuffed into duffel bags, said a source close to the investigation who spoke on condition of anonymity because the investigation was still going on.
At a news conference, FBI agent Richard DesLauriers, FBI agent in charge in Boston, confirmed that investigators had found pieces of black nylon from a bag or backpack and fragments of BBs and nails, possibly contained in a pressure cooker. He said the items were sent to the FBI for analysis at Quantico, Va.
Pressure-cooker explosives have been used in international terrorism, and have been recommended for lone-wolf operatives by Al-Qaida's branch in Yemen. But information on how to make the bombs is readily found online, and U.S. officials said Americans should not rush to judgment in linking the attack to overseas terrorists.
The bombs exploded 10 or more seconds apart, tearing off victims' limbs and spattering streets with blood, instantly turning the festive race into a hellish scene of confusion, horror and heroics.