Uber’s self-driving cars have suffered another setback as a crash in Arizona has left one of the vehicles on its side.

The ride haling business has announced that it will be postponing its commercial autonomous car project, in the wake of the traffic accident in Tempe, Arizona.

The Volvo SUV, which was carrying two engineers in the front passenger seats, collided with another car on Friday, leaving three vehicles badly damaged and the self-driving car on its side. No one was seriously injured in the crash.

In a statement, Uber said: “We are continuing to look into this incident and can confirm we had no backseat passengers in the vehicle.”

The crash is believed to have been caused when “another vehicle failed to yield when turning left” in front of the SUV, according to Sergeant Damn DeSpain of the Tempe police department. “The vehicles collided causing the autonomous vehicle to roll on to its side.”

Uber began testing its self-driving cars last December after licenses were revoked by Californian authorities as some of the self-driving vehicles were not registered as test vehicles.

Following the crash, questions have been raised as to whether the car’s front sensor should have detected the oncoming car quickly enough, and whether the car’s human drivers had enough time to manually avert the danger.

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An investigation into the autopilot system found that it was functioning correctly, with no errors.

Uber was not one of the first companies to begin work on self-driving cars, but last year they were the first to announce that they would begin carrying paying customers in highly autonomous vehicles.

This incident is the latest in a slew of bad news for Uber, as the company finds itself mired on controversy surrounding systemic sexism, CEO Travis Kalanick was recorded berating one of his drivers, a lawsuit with Waymo, and reports that the company was using software to evade law enforcement within the United States.