(CNN) — Investigators scrambling to solve the fatal bombings at the Boston Marathon want to question a man seen on video as a possible suspect in the attack, two official sources with knowledge of the investigation said Wednesday.
The sources identified the person as a man wearing 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. The second source said investigators have not identified this person.
The news comes on a day when authorities have 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.
In addition, a federal law enforcement source told CNN that “anyone who says ‘arrest’ is ahead of themselves.”
A Boston law enforcement 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.
Earlier Wednesday, investigators revealed more details about the makeup of the bombs, which exploded 12 seconds apart near the finish line of the Boston Marathon. The blasts killed three people and wounded about 180 others.
One of the bombs was 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 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.