Uber Technologies Inc. said on Saturday it is suspending testing of its autonomous vehicles after one of the autos was involved in an accident in Tempe, Ariz., a dramatic halt to one of the most high-profile self-driving programs.

The ride-hailing company is pulling vehicles from streets in Pittsburgh, Tempe and California while it investigates the incident in which a Volvo XC90 sport-utility vehicle operated by Uber was upended.

Tempe Police Sgt. Josie Montenegro said the Uber vehicle wasn’t responsible for the accident and that a regular vehicle failed to yield. She said no serious injuries were reported.

The Uber vehicle was in self-driving mode with no customers on board when the incident occurred. “We are continuing to look into this incident,” an Uber spokeswoman said.

Like many technology companies, including rival Alphabet Inc.’s Waymo, Uber is investing heavily in self-driving vehicles with the belief they will reduce fatalities and improve fuel and traffic efficiency by limiting human error.