Boston blasts: 'No known additional threats' in city, FBI says

BOSTON, Massachusetts (AFP) - There are no known additional threats following the bombing at the Boston marathon that killed three people and wounded more than 150, an FBI official said on Tuesday.

FBI Special Agent Rick DesLauriers told reporters in the aftermath of Monday's attack that there were ongoing investigations in various locations throughout the area.

But "there's no known imminent physical threat at any location where we might be conducting investigative activity right now," he said.

Massachusetts Governor Deval Patrick, meanwhile, said only two bombs were used, and no other other unexploded devices had been found despite earlier reports to the contrary.

"It's important to clarify that two and only two explosive devices were found yesterday," Patrick said.

"Other parcels - all other parcels in the area of the blast have been examined. No unexploded bombs. No unexploded explosive devices (were) found." He said over 150 people were injured, some of them gravely.

"Our thoughts go out to all of those injured and killed," he said.

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