Investigators are poring over a wealth of evidence to find out who tried to detonate a car bomb in Times Square - New York's bustling entertainment area.
The bomb, described as "amateurish", consisted of propane tanks, fireworks, petrol and a clock device. It was planted in a sports utility vehicle.
NYC police commissioner Ray Kelly said there was no evidence to support a Taliban link to the bomb attempt.
It followed a claim by the Pakistani Taliban early on Sunday.
In a video message purportedly released by the Pakistani Taliban, the militants said it was a revenge attack for the deaths of its leader and the leader of al-Qaeda in Iraq.
At a news conference on Sunday, Mr Kelly said the device in the Nissan Pathfinder consisted of two clocks connected by wires to a can, which they believed was the detonator, propane tanks and a gun locker.
Mr Kelly also said a white man in his 40s was seen removing a dark shirt in the area and putting it in a bag.
The commissioner added that police would shortly speak to a person in Pennsylvania who believed he may have recorded the man on a video camera.
Experts still had a huge amount of camera footage to pore over, Mr Kelly said.
"It's not easy to go through these tapes. I think we had 82 cameras in the area - we've looked at 30 of those cameras. Three of them had some value," he said.
Earlier on Sunday, US Homeland Security Chief Janet Napolitano said so far there was no evidence that it was more than a "one-off event".
But she added that it was regarded as "a potential terrorist attack".
The vehicle has been sent to a forensic lab in the city's Queens district, after police had conducted a controlled explosion to make it safe, and Times Square was reopened.
Part of the district - where many theatres are sited - had been sealed off on Saturday night after the bomb alert.
"There are forensics in terms of video or possible video that might exist. There is a lot of evidence being tracked down by a lot of people right now," Ms Napolitano said.
Both US President Barack Obama and New York City Mayor Michael Bloomberg praised the quick response by the New York Police Department.
"We are very lucky," Mr Bloomberg told reporters. "We avoided what could have been a very deadly event."
He said the bomb "looked amateurish", but could have exploded, adding that the incident was a "reminder of the dangers that we face". "We have no idea who did this or why," he said.
Police believe the intention was to ignite a fireball.
He said he alerted a passing mounted police officer.
"That's when the smoke started coming out and then we heard the little pop, pop, pop - like firecrackers going out and that's when everybody scattered and ran back," he told the Associated Press. "We dodged a bullet here," he added.
Police shut down several blocks of Times Square, as well as subway lines, while a robotic arm broke windows of the vehicle.
"There were explosive elements, including powder, gasoline, propane and some kind of electrical wires attached to a clock," police spokesman Paul Browne said.
"No motive has been identified," he added.
Police 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 junkyard.
Most Broadway shows went ahead despite the alert.
On everyone's mind is the city's darkest day, the September 2001 attack on the Twin Towers just a few miles away, says the BBC's Barbara Plett in New York.
The most recent terror alert in New York City involved a plot to set off suicide bombs in the subway system.
Earlier this year an Afghan immigrant, Najibullah Zazi, and an associate, Zarein Ahmedzay, both pleaded guilty in connection with the attempt.
Last year four New Yorkers went on trial accused of plotting to bomb synagogues in the city and fire missiles at military aircraft.
