BOSTON -- Authorities are continuing to seek those responsible for the two explosions that killed three and injured more than 170 people at the Boston Marathon finish Monday afternoon.
Richard DesLauriers, special agent in charge of FBI's Boston office, said at a news conference with Massachusetts Gov. Deval Patrick and Boston Mayor Thomas Menino on Tuesday that he wasn't aware of any known physical threats to the marathon before the race, or afterward. Law enforcement had conducted a sweep for explosive devices the morning of the marathon and then an hour before the first runners reached the finish, said Boston Police Commissioner Edward Davis. But that area is open and the public has unrestricted access -- people can come and go, Davis said.
Thirty forensic specialists and explosive experts from the ATF were on the scene, said Gene Marquez, special agent in charge. They were investigating the two explosions -- there were no other bombs or un-exploded devices, he said.
There were no answers about possible suspects or whether anyone was in custody.
All officials urged the public to come forward with photos and video from the scene and surrounding area when the explosion occurred.
Police have obtained the surveillance videos from the area, and surrounding blocks, a crime scene that extended 15 blocks on Monday and was reduced to 12 blocks Tuesday.
The investigation, though, is spreading outside the city of Boston, to eastern Massachusetts, and DesLauriers said, worldwide. People should expect a heightened police presence in the city, at the MBTA, and Logan Airport, for the public's comfort, said State Police Superintendent Timothy Alben.
They praised the fast response of the city's first-responders, police, firefighters and marathon volunteers, who ran to help the injured, and probably saved lives.
"This is a close-knit place, the city of Boston. We know our neighbors, we grieve for them. We know our heroes also, the men and women who wear the badges," said Menino, sitting in a wheelchair at the podium. "This is Boston. We're strong. We will get through this."