This article is by Michael M. Grynbaum, William K. Rashbaum and Al Baker.

Law enforcement officials offered a more detailed description of the makeup of the failed car bomb found in Times Square on Saturday night, and said they were reviewing surveillance footage that showed a white man who appeared to be in his 40s walking away from the area as he looked over his shoulder and removed a layer of clothing.

Raymond W. Kelly, the New York City police commissioner, said on Sunday that the materials found in the Nissan Pathfinder — gasoline, propane, firecrackers and simple alarm clocks — also included eight bags of a granular substance, later determined to be nonexplosive grade of fertilizer, inside a 55-inch-tall metal gun locker.

The bomb, Mr. Kelly said, “would have caused casualties, a significant fireball.”

Had it exploded, said Paul J. Browne, the Police Department’s chief spokesman, “It would have been, in all likelihood, a good possibility of people being killed, windows shattered, but not resulting in a building collapse.”

While the authorities said they were treating the failed bombing — described as a “one-off” by Janet Napolitano, the homeland security secretary — as a potential terrorist attack, they said there was no evidence of a continued threat to the city.