SHANGHAI, May 14 (Reuters) - Chinese robotaxi operator Pony.ai said on Wednesday that one of its cars caught fire while being handled by service staff after a system malfunction, but that no passengers were onboard.

The vehicle was operating without a human driver on the road on Tuesday morning when it showed an "abnormal status", prompting the vehicle's safety protection mechanism to initiate an emergency stop, Pony.ai said.

"No collision occurred and no one was injured. Service personnel arrived at the scene within two minutes upon receiving the alert. During the handling process, the vehicle caught fire," it said in a statement.

"The specific cause is currently under investigation."

The incident could fuel further concerns over the safety of autonomous driving in China. Chinese regulators have recently moved to tighten the marketing and promotion of such features following a fatal accident involving a Xiaomi 1810.HK car that had been on autopilot mode.

One video posted on Chinese social media on Wednesday showed plumes of black smoke billowing from a road in Beijing as cars continued to drive in the reverse direction on a three lane motor way.

Later, it showed emergency personnel putting out a fire of a burnt out car that had mounted a road divider. The poster of the video said it belonged to Pony.ai. Other photos and videos of the car posted online showed that it bore the logo of a Lexus, a luxury car brand of Japan's Toyota 7203.T which is a backer of Pony.ai.

Reuters was unable to independently verify the social media posts and it was unclear from the videos and photos posted online which Lexus model it was.

Qingdao city's radio and television station published an interview on Wednesday with an unidentified Beijing traffic police officer who said that the Pony.ai car caught fire when the engine was ignited for a restart.

Pony.ai did not immediately respond to a request for further comment. Toyota did not immediately respond to a request for comment.

China has for years been encouraging progress in autonomous driving technology and has granted robotaxi operators including Pony.ai and Baidu 9988.HK permits to deploy robotaxis without humans in the driving seat on some open Chinese roads.

Last year, an incident in San Francisco involving a crowd setting on fire an autonomous Waymo robotaxi which had driven into streets crowded with revellers sparked a debate about the ability of robotic cars to make judgments.

(Reporting by Zhang Yan and Brenda Goh. Additional reporting by Daniel Leussink in Tokyo. Editing by Mark Potter)

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