Investigators with BC's Independent police watchdog are looking into an early-morning crash in Langley.
The Independent Investigations Office says RCMP report the crash happened around 2:00.
Mounties say an unmarked police vehicle was responding to a complaint.
It was travelling along 200th Street when it collided with a vehicle that reportedly pulled out of Bryden Avenue.
The driver of the other vehicle was taken to hospital with serious injuries.
Two passengers and a mountie were also injured.