Uber is "likely" not at fault in a crash by one of its self-driving cars that killed a 49-year-old woman, police say.

The accident, in Tempe, Arizona, is believed to be the first time an autonomous vehicle has killed a pedestrian.

Police investigators have video footage of the crash, though it has not been released to the public.

Uber is "likely" not at fault in a first-of-its-kind fatal self-driving-car crash on Sunday in Tempe, Arizona, the local police chief has said.

On Sunday night, one of the transportation company's vehicles operating in autonomous mode struck and killed Elaine Herzberg, 49, in what is believed to be the first time a self-driving vehicle has killed a pedestrian.

Speaking to the San Francisco Chronicle, Tempe police chief Sylvia Moir said, "I suspect preliminarily it appears that the Uber would likely not be at fault in this incident."

There is video of the crash, which investigators are examining but have not released to the public.

"It's very clear it would have been difficult to avoid this collision in any kind of mode [autonomous or human-driven] based on how she came from the shadows right into the roadway," Moir said. Police previously said Herzberg was not using a crosswalk.

There was a vehicle operator in the driver's seat at the time of the crash, and "the driver said it was like a flash, the person walked out in front of them," she said. "His first alert to the collision was the sound of the collision."

But she reportedly added: "I won't rule out the potential to file charges against the [backup driver] in the Uber vehicle."

Tempe Police Department did not immediately respond to Business Insider's request for comment.

The vehicle was travelling at about 40 mph at the time of the collision, a police spokesperson previously said, and did not appear to slow when Herzberg entered the road.

Uber has halted all its self-driving-car operations while the investigation takes place.

In an earlier statement an Uber spokesperson said: "Our hearts go out to the victim's family. We are fully cooperating with local authorities in their investigation of this incident."