One worker was critically injured when a driverless bus crashed into a tree in Whitby in Ontario Thursday, according to reports.

The vehicle – known both as Olli and the WAVE (for Whitby Autonomous Vehicle Electric) and operated by Durham Region Transit in Whitby – crashed on Watson Street, near the Whitby GO station it services. Durham police said the collision happened at 4 p.m., according to a CTV News report.

The male operator was badly hurt and was taken to a trauma centre, where he remains in life-threatening condition, according to reports.

“There was one operator on board,” said Acting Sgt. George Tudos, according to CBC. “No pedestrians or any passengers so that one person did suffer critical injuries.”

According to Durham Region Transit, the worker on board can manually take control of the vehicle at any time if required.

The cause of the crash is still unknown.