Authorities are conducting a massive hunt for answers into the deadly twin bombings at the Boston Marathon as the investigation entered its second day with no arrests or claims of responsibility.
U.S. President Barack Obama characterized the attack as terrorism on Tuesday but said the motive was not clear.
“Any time bombs are used to target innocent civilians, it is an act of terror,” he said. “What we don’t yet know, however, is who carried out this attack or why, whether it was planned and executed by a terrorist organization – foreign or domestic – or was the act of a malevolent individual.”
The explosives were made of 6-litre pressure cookers packed with shards of metal, nails and ball bearings and placed in black duffel bags on the ground, a person briefed on the investigation said Tuesday.
The person, who spoke on the condition of anonymity because the investigation was ongoing, said law enforcement officials have some of the bomb components but did not yet know what was used to set off the explosives.
The FBI’s chief agent in Boston said investigators are following a number of leads and appealed for the public to hand over any photos or videos that might provide clues.
“We will go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime, and we will do everything we can to bring them to justice,” Rick DesLauriers said.
Three people – including eight-year-old Martin Richard and 29-year-old Krystle Campbell – were killed as two bombs blew up seconds apart at the marathon’s finish line on Monday afternoon. More than 170 people were wounded, with several losing limbs. One 27-year-old man lost both his lower legs.
“We just completed the ugly job that the bomb did,” Dr. George Velmahos, chief of trauma surgery at Massachusetts General Hospital, who spoke generally about surgical amputations.
Boston Police Commissioner Edward Davis said authorities had received “no specific intelligence that anything was going to happen” at the race.
Authorities discounted earlier reports about unexploded devices being found, saying the attacks involved two bombs.
Trauma surgeons who treated the wounded at several hospitals appeared to corroborate the account describing the bombs, saying several victims had a range of metallic shrapnel removed during surgery, including what looked like BB pellets and carpentry nails.
“We’ve removed BBs and we’ve removed nails from kids. One of the sickest things for me was just to see nails sticking out of a little girl’s body,” said Dr. David Mooney, director of the trauma centre at Boston Children’s Hospital.
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.
Late Monday, police searched a Boston-area apartment of a Saudi Arabian student who was injured in the blast, law enforcement sources said. On Tuesday, law enforcement sources briefed on the case said that the evidence was indicating that the Saudi student, who had been temporarily considered a “person of interest” in the investigation, would be cleared of suspicion and was unlikely to shed any light on the attack.
The Pakistani Taliban, which has threatened attacks in the United States because of its support for the Pakistani government, on Tuesday denied any role in the marathon bombings.
The fiery explosions took place about 10 seconds and about 100 metres apart, knocking spectators and at least one runner off his feet, shattering windows and sending dense plumes of smoke rising over the street and through the fluttering national flags lining the route.
The bombings occurred about four hours into the race and two hours after the men’s winner crossed the finish line. By that point, more than 17,000 of the athletes had finished the marathon, but thousands more were still running.
The attack may have been timed for maximum carnage: The four-hour mark is typically a crowded time near the finish line because of the slow-but-steady recreational runners completing the race and because of all the friends and relatives clustered around to cheer them on.
The Boston Marathon is one of the world’s oldest and most prestigious races and about 23,000 runners participated. The race honoured the victims of the Newtown, Conn., shooting with a special mile marker in Monday’s race.
It is held on Patriots Day, which commemorates the first battles of the American Revolution, at Concord and Lexington in 1775.
With reports from The Associated Press and Reuters