Some robotaxi passengers were left stranded in the middle of fast-moving traffic in a major Chinese city after their driverless vehicles stopped running, according to police and media reports on Wednesday.

A preliminary investigation indicates more than 100 robotaxis came to a halt because of a “system malfunction”, police in the city of Wuhan said in a statement, without elaborating. No injuries were reported.

One passenger told Chinese media that their robotaxi stopped after turning a corner. An instruction on a screen read: “Driving system malfunction. Staff are expected to arrive in 5 minutes.” After no one showed up, the passenger pushed an SOS button and was told that staff were on their way. The car door could be opened, so the passenger got out on their own.

It is the first time a mass shutdown of robotaxis has been reported in China. In December, many of Waymo’s self-driving cars came to a stop in San Francisco because of a power outage.

The taxis in Wuhan are operated by Baidu, a major Chinese internet and AI company that is expanding its Apollo Go robotaxi business to overseas locations in Europe and the Middle East. The company did not have any immediate comment.

Police said reports that taxis were coming to a halt started coming in around 9 pm, while media reports said multiple people were rescued.

While some passengers were able to exit their taxis on their own, others were afraid to get out because their vehicle had stopped in the middle lane of a ring road with other vehicles passing on both sides, the reports said. Ring roads are elevated roads without traffic lights designed to move traffic quickly in urban areas.

Baidu operates hundreds of robotaxis in Wuhan, which hosted an early pilot project for the company.

The company, which operates more than 1,000 robotaxis, mostly in China, started a service in Abu Dhabi and Dubai this year and is working with partners to launch service in Britain and Switzerland.