President Barack Obama labelled the Boston Marathon bombings an "act of terror" as US law enforcers continued to investigate whether domestic or foreign attackers were responsible for Monday's two bomb blasts. The two explosions near to the marathon's finishing line left three dead, including an eight-year-old boy, and at least 176 injured.
The FBI and Boston police called on people to share any photographs or video taken in the hours leading up to the two near-simultaneous blasts.
Counterterrorism officials, quoted in the US media, said that the Boston bombs were built using six-litre pressure cookers and black powder or gun powder as the explosive and ball bearings as shrapnel.
Law enforcement officials investigating the explosions believe that at least one of the devices contained shards of metal and ball bearings, and another contained nails.
Both were made from pressure cookers and hidden in black duffel bags on the ground. They were designed to cause as many casualties from flying shrapnel once detonated. Some of the injured had 40 or more fragments of pellets and nail-like shrapnel in their bodies, said Dr George Velmahos, the chief of trauma surgery at Massachusetts General Hospital.
The devises were reported by federal investigators to be crudely designed devices built by someone with an experience in explosives and basic electronic circuitry skills.
Officials were reported as saying that the initial signs suggested that the devices may have been triggered using timing mechanisms or remotely with a mobile phone.
Mr Obama had avoided using the word terrorism in his first remarks on the attacks on Monday but went further with his second televised address about the Boston blasts in less than 18 hours
“This was a heinous and cowardly act, and given what we now know took place, the FBI is investigating it as an act of terrorism,” Mr Obama said.
No motive yet
The president said that law enforcement officials had "no sense of motive yet," noting that any suggestions of the reasons for the attack were "speculation."
“What we don’t yet know, however, is who carried out this attack or why, whether it was planned and executed by a terrorist organisation, foreign or domestic, or was the act of a malevolent individual,” said Mr Obama.
Law officials refused to disclose any possible leads in the investigation and said that no one had been arrested.
The FBI, which is leading the inquiry into the bomb attacks, said that it would be a “worldwide investigation”.
“We will go to the ends of the earth to identify the subject or subjects responsible for this despicable crime,” said Richard DesLauriers, the special agent in charge of the FBI office in Boston.
Police searched the apartment of a Saudi Arabian student injured in the blast on Monday night. Massachusetts State Police confirmed that a search warrant was served but gave no further details.
Calling on the public to assist investigators by sharing images of the blasts, Boston State Police superintendent Timothy Alben said: “There has to be hundreds, if not thousands, of photos and videos.”
Boston police said they were removing videos from shops and businesses within the vicinity of the bomb blasts even as they were removing victims soon after the explosions.
Contradicting widespread reports on Monday that multiple unexploded bombs were found near the end of the marathon route, Massachusetts governor Deval Patrick said that there were only two explosive devices.
Fearful of further attacks, US law enforcement agents remained on heightened alert following one of the most high-profile attacks since the September 2001 attacks on New York City and Washington.
Suspect package
A suspicious package led to the evacuation of a terminal at LaGuardia Airport in New York and a US Airways flight was stopped on the ground at Logan Airport in Boston and diverted to a remote location to allow the authorities to examine a bag.
The president was briefed by his national security team — homeland security secretary Janet Napolitano, FBI director Robert Mueller and Lisa Monaco, his homeland security and counterterrorism adviser.
In his televised statement yesterday, the president praised the responses of the emergency services and the people of Boston.
“The American people refused to be terrorised. What the world saw yesterday in the aftermath of the explosions were stories of heroism and kindness and generosity and love,” he said.
