A leading Norwegian public transport operator has said it will introduce stricter security requirements and step up anti-hacking measures after a test on new Chinese-made electric buses showed the manufacturer could remotely turn them off.

Transport operator Ruter said test results published last week showed that Chinese bus maker Yutong Group had access to their control systems for software updates and diagnostics. “In theory, this could be exploited to affect the bus,” it said.

The tests – with buses driven in underground mines to strip away external signals – were conducted both on brand-new Yutong buses and on three-year-old vehicles from Dutch bus manufacturer VDL, the company said.

It said the tests showed that the Dutch buses did not have the ability to conduct over-the-air software updates, while the Chinese-made buses did.

Yutong did not immediately respond to requests from Associated Press on Wednesday seeking comment.

The Guardian newspaper, which reported on the issue, cited a statement from the Chinese company that said it “strictly complies” with the laws and rules of places where its vehicles operate. The statement said data about its buses was stored in Germany.