Homeland Security Secretary Janet Napolitano says the FBI wants to speak with two men seen in at least one video from the Boston Marathon, but she says she isn't calling them suspects.
Without providing details of the men's appearance or what the video shows, Napolitano told the House Homeland Security Committee on Thursday that "there is some video that raised the question" of two men the FBI would like to interview but said she wouldn't described them as suspects.
Napolitano said it's still unclear whether the bombs that exploded near the finish line of the Boston Marathon were the work of foreign or domestic terrorists. She said the investigation is continuing "apace."
Three people were killed and more than 170 others were injured when the bombs exploded Monday.
From previous story:
The work to identify a bombing suspect from reams of Boston Marathon footage has yielded a possible breakthrough as investigators focus on a man seen dropping off a bag near the site of the second of two deadly explosions.
City Council President Stephen Murphy said investigators saw the image of the man dropping off a bag and matched the findings with witness descriptions of someone leaving the scene. He says he was briefed by Boston police.
President Barack Obama is planning to attend a service honoring the victims Thursday in Boston, where the bombings three days earlier killed three people and wounded more than 170.
Massachusetts Gov. Deval Patrick said he understands frustration that no suspects have been captured, but he said it takes time to complete a thorough investigation.
From the previous story:
Investigators have pinpointed two men as "possible suspects" who were seen in images near the finish line of this week's Boston Marathon -- moments before twin bombs there exploded, killing three and injuring about 180 others -- a law enforcement official said.
A circular sent out Wednesday to federal and state agencies features the photos "in an attempt to identify the individuals," who were described as being of "high interest" to investigators.
One of the men is seen carrying a black backpack. An FBI official earlier said that authorities believe the bombs were placed inside a black nylon backpack or bag.
The source said that authorities had not yet identified the two men by name and that the photographs were not being released to the public for fear of impeding the investigation.
Earlier Wednesday, two official sources with knowledge of the investigation identified a man -- who also hasn't been named -- as a possible suspect in the attack.
Seen on a video, this man wore a white baseball cap. One of the sources added that the cap was on backwards and the man was also wearing a light-colored hooded sweatshirt and a black jacket.
It was not immediately known if this man is one of those alluded to in the photographs distributed to law enforcement officials.
This movement in the investigation came two days after the horrific blast shook the city, during what is traditionally one of its biggest and most beloved events each year.
By Wednesday, authorities had made "significant progress" in the case but no arrests, a federal law enforcement source told CNN's John King.
Sources previously told CNN that a suspect was in custody, but both Boston police and the FBI denied that any arrests had been made.
A Boston law enforcement source told CNN, "We got him," but wouldn't clarify whether that meant a suspect has been identified or arrested. Some federal sources said it was even too early to say investigators had identified the suspect, but several sources in Boston told CNN that they have a clear identification.
Speaking on CNN's The Situation Room, Massachusetts Gov. Deval Patrick said investigators were closer to cracking the case "every hour." But he urged patience with the probe.
"What I would say and I would ask of everyone is we give law enforcement the space to do their work," Patrick said. "When they are ready with a complete picture, they will tell us what that picture is."
He added, "I wish they had nailed the perpetrator within minutes of this catastrophe, but I understand from experience it's going to take some time."
Earlier Wednesday, investigators revealed more details about the makeup of the bombs, which exploded 12 seconds apart. One had been housed in a pressure cooker hidden inside a backpack, the FBI said in a joint intelligence bulletin. The device also had fragments that may have included nails, BBs and ball bearings, the agency said.
The lid of a pressure cooker thought to be used in the device was found on a rooftop at the scene, a federal law enforcement official with firsthand knowledge of the investigation told CNN.
The second bomb was also housed in a metal container, but it was not clear whether it too was in a pressure cooker, the FBI said.
The U.S. government has warned federal agencies in the past that terrorists could turn pressure cookers into bombs by packing them with explosives and shrapnel and detonating them with blasting caps.
Photos obtained by CNN show the remains of a pressure cooker found at the scene, along with a shredded black backpack and what appear to be metal pellets or ball bearings. Scraps of at least one pressure cooker, nails and nylon bags found at the scene were sent to the FBI's national laboratory in Virginia, where technicians will try to reconstruct the devices, the agent leading the investigation said Tuesday.
The pieces suggest each of the devices was 6 liters (about 1.6 gallons) in volume, a Boston law enforcement source said. The recovered parts include part of a circuit board, which might have been used to detonate a device.
A law enforcement official said Monday's bombs were probably detonated by timers. But the FBI said details of the detonating system were unknown.
While the clues moved the investigation forward, they did not make it immediately apparent whether the attack was an act of domestic or foreign terrorism.
"If your experience and your expertise is Middle East terrorism, it has the hallmarks of al Qaeda or a Middle East group," former FBI Assistant Director Tom Fuentes said. "If your experience is domestic groups and bombings that have occurred here, it has the hallmarks of a domestic terrorist like Eric Rudolph in the 1996 Atlanta Summer Olympics bombings."
Fuentes said he has investigated both types of terrorism -- from Iraq to the United States -- and finds the Boston attack has elements of both. "It has the hallmarks of both domestic and international (attacks), and you can see either side of that."