General Motors’ driverless taxis are under scrutiny over reports of injured pedestrians involving the vehicles.

The National Highway Traffic Safety Administration opened a preliminary investigation into whether Cruise taxis are “exercising appropriate caution around pedestrians in the roadway.”

The federal regulator received two recent reports involving the taxis and is also examining video “reports” posted on social media.

It said the reports involve the vehicles “encroaching” on pedestrians in or entering roads, including crosswalks, near the intended traveling route of the taxis. It said the number of such incidents is unknown.

The probe sets out to determine the scope of the potential safety issue and any safety risks. It involves nearly 600 of the taxis.

Cruise operates driverless taxis in San Francisco.

In news reports about the investigation, Cruise says its safety record outperforms human drivers’ safety performance. It says on its website that its taxis have amassed 500,000 driverless miles “without any major incidents.”

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