Marathon explosives made from pressure cookers

Boston, April 16: The explosives that killed three and wounded more than 170 at the Boston Marathon were made of pressure cookers packed with metal and ball bearings, a person briefed on the investigation said.

President Barack Obama said it was unclear whether the bombings were carried out by an international organization, domestic group or a "malevolent individual."

Obama, speaking to reporters at the White House, said authorities still don't know who is responsible and officials said no one had claimed responsibility.

He called the bombing "a heinous and cowardly act" used to target innocent civilians.

The chief FBI agent in Boston vowed "we will go to the ends of the Earth" to find whoever carried out the deadly attack on one of the city's most famous civic holidays, Patriots Day.

A person briefed on the attack, which left the streets splattered with blood and glass, said the explosives were in 6-liter pressure cookers and placed in black duffel bags that were placed on the ground.

The person said the duffel bags contained shards of metal, nails and ball bearings. The person spoke on the condition of anonymity because the investigation was ongoing.

These types of pressure cooker explosives have been used in Afghanistan, India, Nepal and Pakistan, according to a July 2010 joint FBI and Homeland Security intelligence report.

One of the three devices used in the May 2010 Times Square attempted bombing was a pressure cooker, the intelligence report said.

"Placed carefully, such devices provide little or no indication of an impending attack," the report said.

The Pakistani Taliban, which claimed responsibility for the 2010 attempt in Times Square, has denied any role in the Boston Marathon attack.

Richard DesLauriers, FBI agent in charge in Boston, said earlier that investigators had received "voluminous tips" and were interviewing witnesses and were analyzing the crime scene.

A European security official said today initial evidence indicates that the attacks were not the work of suicide bombers.

"So far, investigators believe it was not the work of suicide bombers, but it is still too early to rule it out completely," said the official, who spoke from the United States on condition of anonymity because he was not authorized to speak about the U.S. investigation.

The Pakistani Taliban, which has threatened attacks in the United States because of its support for the Pakistani government, has denied any role in the marathon bombings.

The fiery explosions took place about 10 seconds and about 100 yards apart, knocking spectators and at least one runner off their feet, shattering windows and sending dense plumes of smoke rising over the street and through the fluttering national flags lining the route.

Blood stained the pavement, and huge shards were missing from window panes as high as three stories. Victims suffered broken bones, shrapnel wounds and ruptured eardrums.