The US Attorney General has said that investigators had some good leads into the failed car bombing attempt in New York's Times Square and were still looking for an individual spotted in a surveillance video.
"We have some good leads," Eric Holder said on Monday, referring to a video of a man possibly walking away from the vehicle involved in the failed attempt on Saturday.
"We are following a number of other leads as well."
Police investigators spoke to the registered owner of the vehicle used in the attempt, but have not yet identified anyone as the driver.
Paul Browne, the NYPD's deputy commissioner for public information, did not give further details on the registered owner or confirm whether or not the person was considered a suspect.
Investigators were still looking to speak with a man in his 40s videotaped near the vehicle where the bomb was found.
A surveillance video, made public late on Sunday, shows an unidentified white man taking off his shirt, revealing another underneath, while looking back in the direction of the smoking vehicle and putting the first shirt in a bag.
Michael Bloomberg, the city's mayor, said that the person on the tape may not become a suspect.
"This person happened to be in a position which a camera got a good shot of him, and maybe he had something to do with it but there's a very good chance that he did not. We're exploring a lot of leads."
He said that there were millions of people passing through Times Square.
Bloomberg also reiterated there was no "legitimate" evidence that foreign terrorists were involved.
"There is no evidence that this is tied in with al-Qaeda or any other big terrorist organisation," he said on Sunday.
The NYPD and FBI also were examining "hundreds of hours" of security videotape from around Times Square.
Police said the improvised bomb, made from gasoline and propane, could have sprayed shrapnel and metal parts with enough force to kill pedestrians and knock out windows.
The vehicle was parked on one of America's busiest streets, lined with Broadway theaters and restaurants and full of people out on a Saturday night.
Footage from 82 security cameras in the square in central Manhattan was reviewed at police laboratories.
The bomb, which was discovered after a street vendor saw smoke coming out of a parked car, prompted the evacuation of thousands of people from the square and surrounding areas on Saturday evening.
Raymond Kelly, the police chief, said the amateurish device, had it exploded, would have created a "significant fireball."
The car "would have at least have been cut in half", he said.
Janet Napolitano, the homeland security secretary, said the FBI, the New York police and the government's terrorism task force were probing a "potential terrorist attack."
There was no evidence of a broader plot, but law enforcement authorities had been alerted to "stay on their toes," she said.