A crude car bomb made of propane, gasoline, and fireworks failed to detonate last night in Times Square. No suspects have been identified yet, but from all accounts the device was an amateurish pile of junk.

At 6:28 p.m., Mr. Kelly said, a video surveillance camera recorded what was believed to be the dark green Nissan S.U.V. driving west on 45th Street.

Moments later, a T-shirt vendor on the sidewalk saw smoke coming out of vents near the back seat of the S.U.V., which was now parked awkwardly at the curb with its engine running and its hazard lights on. The vendor called to a mounted police officer, the mayor said, who smelled gunpowder when he approached the S.U.V. and called for assistance. The police began evacuating Times Square, starting with businesses along Seventh Avenue, including a Foot Locker store and a McDonald’s.

Police officers from the emergency service unit and firefighters flooded the area and were troubled by the hazard lights and running engine, and by the fact that the S.U.V. was oddly angled in the street. At this point, a firefighter from Ladder 4 reported hearing several “pops” from within the vehicle. The police also learned that the Pathfinder had the wrong license plates on it.

Members of the Police Department’s bomb squad donned protective gear, broke the Pathfinder’s back windows and sent in a “robotic device” to “observe” it, said Deputy Commissioner Paul J. Browne, the police department’s chief spokesman.

Inside, they discovered three canisters of propane like those used for barbecue grills, two five-gallon cans of gasoline, consumer-grade fireworks — the apparent source of the “pops” — and two clocks with batteries, the mayor said. He said the device “looked amateurish.”

Mr. Browne said: “It appeared it was in the process of detonating, but it malfunctioned.”

Bomb squad officers also discovered a two-by-two-by-four-foot metal box — described as a “gun locker” — in the S.U.V. that was taken to the Police Department’s firing range at Rodman’s Neck in the Bronx to be destroyed, Mr. Kelly said. It was not immediately known what, if anything, was inside it.