Uber said Monday it has paused its testing of autonomous cars, including in Toronto, after a pedestrian fatality overnight in Tempe, Ariz.

A spokesperson for Uber Canada confirmed the company has halted tests in San Francisco, Phoenix, Pittsburgh and Toronto.

Reports from The Associated Press indicate that a self-driving Uber vehicle in Tempe was in autonomous mode with a human operator behind the wheel when it struck a woman who had walked into the street. The woman later died in hospital. She has been identified as Elaine Herzberg, 49.

"The vehicle was traveling northbound … when a female walking outside of the crosswalk crossed the road from west to east when she was struck by the Uber vehicle," Tempe police said in a statement. They later added that she was walking with a bike when she was struck.

The New York Times reported that the fatality could be the first known fatality involving a pedestrian struck by an autonomous vehicle on public roads.

The National Transportation Safety Board in the United States said it is sending a team of four investigators to Tempe.

"The investigation will address the vehicle's interaction with the environment, other vehicles and vulnerable road users such as pedestrians and bicyclists," the NTSB said in a statement, adding that its team will look into vehicle factors, human performance and electronic recorders.

A tweet from Uber chief executive Dara Khosrowshahi expressed condolences to the victim's family. The company says it is co-operating with police and authorities in an investigation of the fatality.

Some incredibly sad news out of Arizona. We’re thinking of the victim’s family as we work with local law enforcement to understand what happened. <a href="https://t.co/cwTCVJjEuz">https://t.co/cwTCVJjEuz</a> —@dkhos

The Ontario Ministry of Transportation said it is reviewing the Tempe incident.

"We will be following the situation in Arizona closely, and will consider what measures are appropriate as more becomes known," ministry spokesman Bob Nichols told Reuters.

Since January 2016, Ontario has allowed the testing of autonomous vehicles on provincial roads. Under the government rules of the pilot project, a driver must remain in the driver's seat of the vehicle at all times and monitor the vehicle's operation. Seven groups have been approved to participate in the 10-year test program.

However, in December 2017, the provincial government sought public comments on a proposal to change the pilot project to allow for driverless testing of fully autonomous vehicles. Participants would have to be approved by the province's Ministry of Transportation. The comment period on the proposal closed on Feb. 4.