BOSTON — In the first major break in the hunt for the Boston Marathon bomber, FBI personnel found security video clips Wednesday that showed a man they believe may have played a role in planting the explosives that killed three people and injured more than 170 on Monday.
The videos also showed at least a handful of others whom the authorities want to question, either because of what they appear to be doing in the video or their proximity to the blasts, according to a senior law enforcement official.
The official said the authorities were trying to boil down the number of people of interest in the videos and will then decide whether to ask the public's help in locating them.
“It's a crowd. There are a lot of different angles — it is not like some television-produced video — there's a lot that isn't clear,” said the official. “But most interpretations support the notion that one man is seen dropping a bag.”
The official said: “There are several videos with people in them, and we're looking to talk to more than one guy. It's still very squishy, but there are a lot of interesting people” the authorities want to talk to.
The breakthroughs came less than 48 hours after the highest-profile act of terror in the U.S. since the 9/11 attacks on New York City and Washington in 2001.
President Barack Obama is getting regular briefings on the investigation and is satisfied with the progress, White House press secretary Jay Carney said at a briefing earlier Wednesday.
“The full weight of the federal government is behind this investigation,” Carney said. “But this investigation is now not even 48 hours old.”
As news spread of the video Wednesday afternoon, officials emphatically denied a flurry of news media reports that they had made an arrest. The FBI was still “looking for a name to put with a face in a video,” one law enforcement official said, speaking on the condition of anonymity.
Those denials did not deter hundreds of office workers and reporters from gathering outside the federal courthouse here, where they anticipated that a suspect would be arraigned. A midday bomb scare caused the courthouse to be evacuated and created confusion as the crowds were moved far away from the building and it was ringed by police vehicles. By nightfall, no arrest had taken place.
At Copley Square, the crime scene, several blocks long, remained barricaded Wednesday as investigators in white hazmat suits scoured the buildings and roofs for pieces of evidence from the two explosions, which occurred at 2:50 EDT Monday afternoon near the finish line of the marathon.
Teams of investigators, including more than 1,000 FBI agents, were tracking possible leads developed Tuesday after they had discovered remnants from the two bombs. Those remnants included parts of one or two kitchen pressure cookers that had evidently been packed with nails, ball bearings and black powder and used as explosive devices; the torn remains of a dark nylon backpack or duffel bag in which one of the bombs had been hidden; and a circuit board, wires and other parts from timing devices. Investigators hoped to track the items back to where they were sold and compile a list of names or descriptions of the buyers.
A piece of the lid of one of the pressure cookers was found on a rooftop near the blast, a law enforcement official said Wednesday — giving a sense of the tremendous force of the explosion.
The possible break in the case came as investigators scrutinized scores of videos and photographs from surveillance cameras from nearby businesses, as well as from smartphone-wielding marathon spectators and television crews that were filming the marathon when the deadly blasts went off. So far, no one has taken responsibility for the attacks.
As the investigation went into a third day, there were signs of jitters around the nation, which was on high alert. New York City officials said there had been an increase in reports of suspicious packages. In Oklahoma City, the scene of a devastating bombing in 1995, City Hall was briefly evacuated Wednesday morning as authorities examined a stolen rental truck that was parked outside. (There was no bomb, officials there said.)
In Washington, parts of two Senate office buildings were shut down as officials investigated reports of suspicious letters or packages, and the Secret Service said that a letter addressed to Obama contained a suspicious substance. It was intercepted at a screening facility outside the White House, and federal agents arrested a suspect Wednesday evening.
In New York City, the Police Department received 143 reports of suspicious packages between Monday afternoon, just after the Boston explosions, and midnight Tuesday. That was an increase of more than 300 percent over a similar time period last year, said Raymond W. Kelly, the police commissioner.
Boston prepared to mourn the victims at an interfaith church service this morning at the Cathedral of Holy Cross. The president and first lady Michelle Obama were scheduled to attend.
The three people killed in the blasts represented a cross-section of Boston, brought together seemingly at random to watch one of the city's proud traditions, the 117th annual marathon. There was Lingzi Lu, in her early 20s, a graduate student at Boston University and one of the thousands of international students drawn to the area's universities. There was Martin Richard, a vivacious 8-year-old third-grader from a well-loved family in Dorchester, a tight-knit Boston community. And there was Krystle Campbell, 29, of Arlington, Mass., a hard-working woman known for her sense of humor who had started working at restaurants as a waitress in high school and had become a restaurant manager.
If investigators in Boston can find a facial image of sufficient quality from the security video, it could provide a powerful lead.
While investigators have focused on the images of the possible suspect, they are continuing to pursue a broad range of other avenues, one law enforcement official said.
“We try not to get tunnel vision about it,” the official said, adding, “we're working a lot of other possibilities.”
This report includes material from Bloomberg News.