An Uber self-driving car hit and killed a woman crossing the street in Arizona, police said on Monday, marking a potential blow to the technology expected to transform transportation.

The ride services company said it was suspending North American tests of its self-driving vehicles.

The accident, which occurred on Sunday, spurred reaction from U.S. lawmakers who have been debating whether to pass legislation that would speed introduction of self-driving cars into the United States.

The Uber vehicle was in autonomous mode with an operator behind the wheel at the time of the accident.

The victim died from her injuries in a hospital, police said.

The U.S. National Highway Traffic Safety Administration (NHTSA) and National Transportation Safety Board (NTSB) said they were sending teams to investigate the crash.

Canada's transportation ministry in Ontario, where Uber conducts testing, also said it was reviewing the accident.

It is no tclear whether the death was caused by an error by Uber's driverless car software. An error in Tesla's Autopilot software contributed to the death of Tesla driver Joshua Brown in 2016, but that crash happened only after the driver ignored repeated warnings to put his hands back on the steering wheel.

Arizona has allowed companies to test self-driving vehicles as a means to economic growth and jobs.

Uber has logged 2 million self-driving miles through December. The company has more than 100 autonomous cars testing on the roads of the greater Phoenix area, the company's prime testing ground.