Following a collision that caused significant damage to an Uber self-driving car in Arizona last week, the company has suspended its autonomous driving experiments in Arizona and Pittsburgh.

A photo on Twitter shows one of the Volvo SUVs fitted with Uber self-driving tech resting on its side near another battered vehicle, suggesting a major collision. A Tempe, Ariz., police spokesperson confirmed the collision in an email to Reuters, explaining that a human-driven vehicle "failed to yield" to the SUV.

BREAKING: Self-driving Uber vehicle on it's side after a collision in Tempe, AZ.

Photos by @fresconews user Mark Beach pic.twitter.com/5NCF2KG0rW — Fresco News (@fresconews) March 25, 2017

"The vehicles collided, causing the autonomous vehicle to roll onto its side," Josie Montenegro told Reuters. "There were no serious injuries."

Following the collision, Uber suspended its US self-driving programs in Tempe, Pittsburgh, and San Francisco, Reuters reports. The company resumed testing in San Francisco on Monday, since that program involves just two vehicles for research purposes and does not accept paying passengers. An Uber spokesperson did not immediately respond to a request for comment.

While self-driving vehicle collisions aren't unheard of, they're typically of the minor fender-bender variety. Google's autonomous test vehicles have been involved in several crashes over the years, including an incident last September when another car ran a red light and collided with a Google SUV. A more serious crash last year left a Tesla driver dead after his car, operating in "Autpilot," collided head-on with a truck.

Last week's collision appears to be the first major crash involving an Uber self-driving car, but the company's self-driving experiment has been mired in controversy before. In December, Uber was forced to suspend its San Francisco self-driving program after it refused to secure a permit from California's Department of Motor Vehicles. The DMV revoked the vehicles' licenses, although the cars returned to the city in January for mapping and research purposes, instead of picking up paying passengers.

The provenance of the company's self-driving technology is also in question, following a lawsuit last month from Google subsidiary Waymo, which alleges that Uber used Google's trade secrets without permission to develop its own self-driving cars. Uber claims the suit is "baseless."