BOSTON, Mass. (NBC) -- Authorities investigating the Boston Marathon bombing said Wednesday they have the face but not the name of someone seen on video leaving a black bag near the scene of the blasts.
The person was seen on a surveillance camera from a Lord & Taylor department store, one official said.
The FBI, Boston police, the U.S. attorney in Boston, a senior White House official and other NBC News sources all said there had not been an arrest. The statements came after several media outlets reported an arrest in the case.
"Despite reports to the contrary there has not been an arrest in the Marathon attack," Boston police said from an official Twitter account.
Authorities are focusing on a video of a man putting a bag down at the location of the bombing at the Boston Marathon.
The FBI added: "Since these stories often have unintended consequences, we ask the media, particularly at this early stage of the investigation, to exercise caution and attempt to verify information through appropriate official channels before reporting."
An official told NBC News that investigators are "zeroing in on some people."
The investigators said they were focused on video taken in the area closest to the blasts, which killed three people and injured 176 near the finish line Monday. Senior officials in Boston also said the team of investigators on the ground is making "solid progress" and that forensics work on bomb parts continues.
Earlier in the day, doctors said they have pulled fragments as large as 2 inches, including pieces of wood, concrete and plastic, from the bodies of people wounded in the attack.
The injuries have been so severe that surgeons have operated a second time on some patients, even after amputations, to fight possible infection, said Dr. Peter Burke, the chief of trauma services at Boston Medical Center.
Investigators have said the two bombs were housed in metal containers — at least one a kitchen pressure cooker — and studded with metal, including fine nails or brads, to make the devices more lethal. Burke said that doctors are making the fragments available to police.
A 5-year-old boy was among the patients still in critical condition at the hospital, Burke said. In all, 69 patients were still at Boston hospitals, including 19 critically injured.
FBI bomb technicians returned to the scene of the explosions Wednesday with police dogs.
On Tuesday, investigators said their hunt for suspects and a motive in the marathon attack was "wide open" and disclosed the first details about the two bombs — saying that they were concealed in bags.
The lead investigator for the FBI, Richard DesLauriers, made an passionate plea for help from the public: "Someone knows who did this."
The devices appear to have been delivered to the marathon course in duffel bags.
-- By Richard Esposito, Pete Williams and Erin McClam, NBC News
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