A photo posted on Fresco News' Twitter feed showed a self-driving Uber Volvo SUV on its side. Fresco News/Mark Beach

A self-driving Uber car was involved in an accident on Friday night in Tempe, Arizona, in one of the most serious incidents to date involving the growing fleet of autonomous vehicles being tested on US roads and prompting Uber to suspend autonomous-car testing in the state.

A photo posted on Fresco News' Twitter feed showed a self-driving Uber Volvo SUV on its side.

Another car, in the background, is pictured with dents and smashed windows. Nobody was seriously injured in the incident.

The Uber SUV was operating in autonomous mode when the accident occurred, Uber confirmed to Business Insider. Uber has halted its self-driving-car pilot in Arizona and is investigating what caused the incident.

"We are continuing to look into this incident and can confirm we had no backseat passengers in the vehicle," an Uber representative said in an email to Business Insider.

A Tempe police representative told Bloomberg that the Uber was not at fault in the accident and was hit by another car that failed to yield.

Still, the collision will likely to turn up the temperature on the heated debate about the safety of self-driving cars.

A Tesla operating in Autopilot mode crashed into a truck last year, killing the car's driver.

Google's prototype self-driving cars have been involved in several fender-benders over the years, though most were operating in manual mode at the time of the incidents.

Automakers and tech companies are rushing to develop and test self-driving cars, which some people think could eventually replace traditional cars. But there are many questions about the safety and reliability of the technology that regulators are still grappling with.

Problems at the DMV

Uber launched its self-driving-car pilot in Arizona in December after a dispute with California regulators over the program.

Uber attempted to launch the program (similar to the one in Pittsburgh) in mid-December in California. But Uber neglected to obtain an autonomous-vehicle license before the launch, and that led the California DMV to revoke registration of the company's 16 autonomous vehicles.

Uber then shipped all 16 of its self-driving Volvo XC90s to Arizona on the back of its self-driving Otto truck.

Uber's autonomous pilot program ran in California for just a week, but the company's self-driving Volvo was caught on video running through a red light on a busy intersection in front of the city's Museum of Modern Art.

An Uber representative said at the time that the incident was the result of human error, but internal sources told The New York Times the Uber was driving itself when the incident happened.

An Uber self-driving vehicle climbs a hill in San Francisco. Uber

Uber is involved in a lawsuit over its self-driving technology.

Waymo, Alphabet's self-driving-car company, is suing Uber, alleging that the ride-hailing service stole the designs for its lidar system. Lidar sensors shoot lasers and allow self-driving vehicles to detect obstacles. Waymo filed an injunction asking a federal judge to freeze Uber's use of its self-driving tech.

Uber has been under intense scrutiny after a string of scandals.

The company has been accused of promoting a sexist workplace after former engineer Susan Fowler wrote a blog post detailing allegations of harassment and gender bias she said she experienced at the company.

The New York Times posted a bombshell report detailing a company retreat where a manager groped several female employees and was later fired.

Uber used a secretive tool called Greyball to evade government official and regulators at a time when city regulators were trying to block the ride-hailing service.