Ride-hailing firm Uber is pausing tests of its self-driving cars in four North American cities while police and federal investigators probe a fatal accident involving one of them.

The death, in Tempe, Ariz., occurred shortly after 10 p.m. local time on Sunday, when a 49-year-old woman walking outside of a crosswalk to get from one side of a street to the other was struck by an Uber vehicle in self-driving mode, police said.