Terror returns to America,FBI begins probe in Boston Marathon bombings

“This was a heinous and cowardly act,” Obama said. “And given what we now know about what took place,the FBI is investigating it as an act of terrorism. Any time bombs are used to target innocent civilians,it is an act of terror. 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.”

Two powerful bombs exploded near the finish line of the marathon on Monday afternoon,as one of this city’s most cherished rites of spring was transformed from a scene of cheers and sweaty triumph to one of screams and carnage.

Among the three dead was an 8-year-old boy,Martin Richard,who had been watching the marathon with his family. His mother and a sister were badly injured. The names of the other two victims have not been made public.

Surgeons at Boston hospitals told televised news conferences on Tuesday that the bombs contained small pellets and sharp “nail-like” objects that were designed to maim their victims.

Two congressional officials who were briefed by federal authorities separately said that at least one bomb,and probably both,were pressure cookers filled with shrapnel — nails,metal pellets and ball bearings — that had been packed in a bag or backpack of some kind and placed on the ground,perhaps to look like trash or someone’s personal bag.

Representative Stephen Lynch,Democrat of Massachusetts,said doctors had identified material lodged in a survivor’s leg as a ball bearing. “This is not a device like (the one that killed 150 people in) Oklahoma City (in 1995),” he said. “That was to bring the building down. The ball bearings are meant as anti-personnel munitions. They’re trying to cause carnage here.”

Representative Michael McCaul,a Texas Republican who heads the House Homeland Security Committee,said authorities believe the explosive may have been similar to improvised explosive weapons that have been used against American troops in Iraq and Afghanistan.

An explosive device fashioned from a pressure cooker was used in the attempted bombing of Times Square in New York in 2010.

Late Monday night,law enforcement officials descended on an apartment building in the suburb of Revere,about five miles north of Boston’s Copley Square,linked to a man the police took into custody near the scene of the bombings.

But on Tuesday morning,one law enforcement official said investigators had determined that the man,who was hurt in a blast and was questioned at the hospital,was not involved in the attack.

The authorities have not announced any arrests and,so far,no one has claimed responsibility as the police conduct what they have said is “a criminal investigation that is a potential terrorist investigation”.

Law enforcement officials pleaded at a briefing Tuesday morning for anyone who took pictures or video of the finish line at the time of the blast to submit them to the FBI. The police also said they were examining footage from nearby security cameras frame by frame as they continue their search for the identity of the person or persons who placed the bombs near the end of the 26.2-mile course.

Almost three-quarters of the 23,000 runners who participated in the race had already crossed the finish line when a bomb exploded around 2.50 pm in a haze of smoke amid a crowd of spectators on Boylston Street in the heart of the city. Thirteen seconds later,another bomb exploded several hundred feet away.

On Tuesday morning,officials said that the only explosive devices found were the ones that exploded — clarifying conflicting statements that were given on Monday in the chaotic aftermath of the blasts,when some officials said that other devices were found.

Some law enforcement officials had noted on Monday that the blasts came at the start of a week that has sometimes been seen as significant for radical American anti-government groups: it was the April 15 deadline for filing taxes,and Patriots’ Day in Massachusetts,the start of a week that has seen violence in the past. April 19 is the anniversary of the 1995 Oklahoma City bombing.

The Boston Marathon,one of running’s most storied events which typically draws half a million spectators,is held on the third Monday of April every year. The men’s race was won by Lelisa Desisa Benti of Ethiopia,who finished it in 2 hours,10 minutes and 22 seconds,but long after the world-class athletes had left,the sidewalks were thick with spectators cheering on friends and relatives as they loped,exhausted,toward the finish line.

The blast was so powerful that it blew out shop windows and damaged a window on the third floor of the Central Library in Copley Square. Dr Alasdair Conn,chief of emergency services at Massachusetts General Hospital,said several people brought in had lost their legs.

“This is like a bomb explosion we hear about in Baghdad or Israel or other tragic points in the world,” Conn said.