The impact shattered windows, damaged cars and sent crowds running from the scene at an hour when Chelsea, always a popular destination, was filled with residents and tourists.

“It was the biggest blast I ever would imagine, lights flashing, glass shattering,” said a woman who was injured in the explosion.

The force of the explosion, she said, flung her into the air.

“It happened so fast I was thrown up and landed down, I didn’t know where it had come from,” said the woman, who would give only her first name, Helena, as she hobbled out of Bellevue Hospital Center about 4 a.m. after she was treated for injuries to her eye and legs. “I realized there was blood streaming down my face, and I couldn’t see out of my eye.”

Luke McConnell, who was visiting from Colorado, was headed toward a restaurant on West 27th Street when the blast occurred. “I felt it, like a concussive wave, heading towards me.”

“Then there was a cloud of white smoke that came from the left side of 23rd Street near Sixth,” he said. “There was no fire, just smoke.”

Witnesses said they could feel the explosion from several blocks away. Daniel Yount, 34, said he was standing on the roof of a building at 25th Street and the Avenue of the Americas with friends.

“We felt the shock waves go through our bodies,” he said.

It was a startling scene, full of dark possibilities, for a city that endured the attacks of Sept. 11, 2001, but has so far been spared the kind of mayhem that has terrorized city after city around the world in the 15 years since.

The closest New York has come to an attack was in 2010, when the police found a crude car bomb of propane, gasoline and fireworks inside a sport utility vehicle in Times Square. Although the device had apparently started to detonate, there was no explosion.

On Saturday night in Chelsea, the device found on West 27th Street also caused no harm.

Images shared on social media and confirmed as authentic by a senior police official showed a silver-colored piece of cookware with wires and a cellphone attached.

The official said the Police Department’s bomb squad was taking the device to a department facility in the Bronx, where robots would inspect it.