New York police found a suspected car bomb in a smoking sport utility vehicle Saturday evening in Times Square, then cleared the streets of thousands of tourists milling in the landmark district so they could dismantle the device.

A white robotic police arm broke windows of the black Nissan Pathfinder to remove any explosive materials while heavily armed police and emergency vehicles shut down the city's busiest streets, teeming with taxis and theatregoers on one of the first summer-like evenings of the year.

Investigators removed bomb-making materials, including propane tanks, explosive powders and a crude timing device, top police spokesman Paul Browne said.

"There were explosive elements, including powder, gasoline, propane and some kind of electrical wires attached to a clock," Browne said early Sunday. "No motive has been identified."

An officer noticed smoke coming from the SUV around 6:30 p.m. ET and police cleared the streets.

Officials are investigating a report that someone was seen running from the vehicle at some point and are reviewing security videotapes, Browne said. The Nissan Pathfinder's licence plates do not match the car's registration, he said.

Police evacuated several residential and commercial buildings and cleared the streets of people. Officers were deployed around the area with heavy weapons on empty streets in the heart of midtown Manhattan.

Some tourists reported hearing a small explosion hours after the car was first located.

Shelly Carlisle of Portland, Ore., said police crowded into her Broadway theatre after the curtain closed on Next to Normal, a show on the same block where the SUV was found.

"At the end of the show, the police came in. We were told we had to leave," Carlisle said. "They said there was a bomb scare."

The car was parked on 45th Street, and the block was closed between Seventh and Eighth avenues as a precaution, police said.

Times Square is about 6.5 traffic-choked kilometres north of the site where terrorists bombed the World Trade Center in 1993, then laid waste to it on Sept. 11, 2001.

'I've never seen anything like it': tourist

FBI agents are on the scene with the New York Police Department, and the matter is being taken seriously, said Paul Bresson, head of the FBI's public affairs office at bureau headquarters in Washington.

The Homeland Security Department is aware of the situation, but the NYPD has it under control and is investigating, said a Homeland Security official who spoke on condition of anonymity because the investigation is in progress.

The block that was closed is one of the prime blocks for Broadway shows, with seven theatres housing such big shows as Billy Elliot and Lend Me a Tenor.

God of Carnage and Red began about a half hour later than usual, but the shows were not cancelled, said spokesman Adrian Bryan-Brown.

Katy Neubauer, 46, and Becca Saunders, 39, both of Milwaukee, were shopping for souvenirs two blocks south of the SUV when they saw panicked crowds.

"It was a mass of people running away from the scene," Neubauer said.

Said Saunders: "There were too many people, too many cops. I've never seen anything like it."

Mayor Michael Bloomberg left early from the White House correspondent's dinner Saturday night. A news conference was planned in New York for early Sunday.

President Barack Obama, who attended the annual dinner, praised the NYPD's quick response, the White House said. He has also directed his homeland security and counterterrorism adviser, John Brennan, to advise New York officials that the federal government is prepared to provide support.

Brennan and others will keep Obama up to date on the investigation, the White House said.

In December, a van without licence plates parked in Times Square led police to block off part of the area for about two hours. A police robot examined the vehicle, and clothes, racks and scarves were found inside.

In March 2008, a hooded bicyclist hurled an explosive device at a military recruiting centre in the heart of Times Square, producing a flash, smoke and full-scale emergency response. No suspect was ever identified.

In December, police ordered thousands of holiday tourists out of Times Square after finding a white van with blacked-out windows, but no licence plates, that had been parked there for days. No bombs were found and police later said they overlooked the van because it contained a parking placard for a nonprofit police group.