Police have been gathering evidence from the SUV that contained the bomb. Photo by bbc.co.uk
There is no evidence the failed attempt to detonate a car bomb in New York was the work of al-Qaeda or any other big terrorist group, the city's mayor says.
Michael Bloomberg spoke after police dismissed claims by a Pakistani Taliban group that it was responsible.
Investigators are hunting a middle-aged white man seen removing his shirt near the scene at Times Square on Saturday evening and stuffing it into a bag.
President Barack Obama has vowed the US will track down the perpetrators.
Investigators have been gathering evidence from the Nissan Pathfinder in which the homemade petrol and propane bomb was found.
Police are also examining a home video taken by a tourist of a man seen near the car.
Detectives have established that the car's registration plates do not match up with the Nissan.
They belonged to a car owner in the state of Connecticut, who told officers he had sent the plates to a scrap-yard.
A Pakistani Taliban group claimed in a one-minute internet video that it was behind the failed attack.
Tehreek-e-Taliban said the bomb was revenge for the deaths of its leader and the leader of al-Qaeda in Iraq.
But the police commissioner and the mayor cast doubt on the claim.
"There is no evidence that this is tied in with al-Qaeda or any other big terrorist organisation," Mr Bloomberg said.
The mayor earlier told reporters New York had avoided what could have been "a very deadly event".