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No further Boston threat, says FBI No further Boston threat, says FBI
(35 minutes later)
The FBI has said there are "no known additional threats" in Boston following the bombing of the marathon.The FBI has said there are "no known additional threats" in Boston following the bombing of the marathon.
At a news briefing, officials said no bombs other than the two which exploded had been found, but that no-one was being held over the attack.At a news briefing, officials said no bombs other than the two which exploded had been found, but that no-one was being held over the attack.
Three people were killed, including an eight-year-old boy, and more than 150 injured by the bombs.Three people were killed, including an eight-year-old boy, and more than 150 injured by the bombs.
Doctors treating the wounded have said a number of people have had pellets and "nail-like" fragments removed.Doctors treating the wounded have said a number of people have had pellets and "nail-like" fragments removed.
George Velmahos, chief of trauma surgery at Massachusetts General Hospital, where many of the wounded are being treated, said he believed such fragments had come from inside the bomb. The FBI are investigating the bombing as possible terrorism.
Some patients had more than 40 shrapnel wounds, he said, adding that his hospital had carried out four amputations. In Washington, President US Obama described it as a "heinous and cowardly act".
US President Barack Obama is due to give a news briefing at 11:30 Washington DC time (16:30 BST). "Any time bombs are used to target innocent civilians it is an act of terror", he said.
'Cruel act of terror' But he stressed that it was not yet known which group or individual was behind the attack, saying "everything else at this point is speculation".
"It will take time... but we will find whoever harmed our citizens and we will bring them to justice," he said.
Two devices
Richard DesLauriers, the FBI agent in charge of the investigation, told reporters in Boston there was "no known imminent physical threat at any location where we might be conducting investigative activity right now".Richard DesLauriers, the FBI agent in charge of the investigation, told reporters in Boston there was "no known imminent physical threat at any location where we might be conducting investigative activity right now".
He said the FBI was "not aware of any threat information prior to the marathon".He said the FBI was "not aware of any threat information prior to the marathon".
Police had received "voluminous tips" from the public, he said, urging people to co-operate with investigators.Police had received "voluminous tips" from the public, he said, urging people to co-operate with investigators.
"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," he said."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," he said.
The governor of Massachusetts, Deval Patrick, said it was "important to clarify that two, and only two, explosive devices were found yesterday".The governor of Massachusetts, Deval Patrick, said it was "important to clarify that two, and only two, explosive devices were found yesterday".
There were earlier reports that several unexploded devices had been found across the city.There were earlier reports that several unexploded devices had been found across the city.
Mr Patrick said all other suspect parcels had been examined and found not to be bombs.Mr Patrick said all other suspect parcels had been examined and found not to be bombs.
Timothy Alban of the Massachusetts State Police appealed to members of the public to send in any footage they had from the day.Timothy Alban of the Massachusetts State Police appealed to members of the public to send in any footage they had from the day.
"There have to be hundreds if not thousands of photographs or videos or observations that were made down at that finish line yesterday. And they're sitting out there amongst everyone that's watching this event this morning," he said."There have to be hundreds if not thousands of photographs or videos or observations that were made down at that finish line yesterday. And they're sitting out there amongst everyone that's watching this event this morning," he said.
"You might not think it's significant but it might have some value to this investigation.""You might not think it's significant but it might have some value to this investigation."
Officials praised emergency workers and volunteers who had helped those injured, saying they had saved lives.Officials praised emergency workers and volunteers who had helped those injured, saying they had saved lives.
George Velmahos, chief of trauma surgery at Massachusetts General Hospital, where many of the wounded are being treated, said some people had arrived with more than 40 shrapnel wounds.
"Many of them have severe wounds, mostly in the lower part of their bodies, wounds related to the blast effect of the bomb, as well as small metallic fragments that entered their body - pellets, shrapnel, nails," he said.
He said the bombs had probably contained "multiple metallic fragments", and that the hospital had carried out four amputations.
Child killed
The first of the explosions went off close to the finishing line at about at 14:50 local time (18:50 GMT) on Monday.The first of the explosions went off close to the finishing line at about at 14:50 local time (18:50 GMT) on Monday.
Then seconds later, as rescuers were rushing to help the injured, another explosion went off about 170m away from the first blast.Then seconds later, as rescuers were rushing to help the injured, another explosion went off about 170m away from the first blast.
Details of those killed have been officially released, but eight-year-old Martin Richard, from Boston, has been named as one of those killed.Details of those killed have been officially released, but eight-year-old Martin Richard, from Boston, has been named as one of those killed.
His mother and sister were also injured as they waited for his father to finish the race.His mother and sister were also injured as they waited for his father to finish the race.
On Monday, Mr Obama had said those behind the attack "will feel the full weight of justice".
"We will find out who did this. We'll find out why they did this," he said.
Although he did not use the word "terrorism", a White House official later said: "Any event with multiple explosive devices - as this appears to be - is clearly an act of terror, and will be approached as an act of terror."
US Defense Secretary Chuck Hagel on Tuesday said it had been "a cruel act of terror".
The annual Boston Marathon this year had a field of about 23,000 runners and was watched by hundreds of thousands of spectators.The annual Boston Marathon this year had a field of about 23,000 runners and was watched by hundreds of thousands of spectators.
It is held on Patriots' Day, a Massachusetts state holiday which commemorates the first battles of the American Revolution in 1775.It is held on Patriots' Day, a Massachusetts state holiday which commemorates the first battles of the American Revolution in 1775.
British police said they were reviewing security plans for Sunday's London Marathon - the next major international marathon - but that it was going ahead, saying they were "very, very well-practised" at managing big events.British police said they were reviewing security plans for Sunday's London Marathon - the next major international marathon - but that it was going ahead, saying they were "very, very well-practised" at managing big events.