Ontario Provincial Police say eastbound Hwy 401 at Comber Sideroad has reopened after a collision Saturday afternoon.
OPP Constable Jim Root says one of their cruisers was struck from behind while it was pulled on the shoulder of the highway.
An officer, who had been working with the OPP's Essex County Traffic Management Unit, was taken to hospital with injuries. Root says the officer's injuries are not life-threatening
The vehicle that struck the cruiser, a Volkswagen, had five occupants. Four of them were sent to hospital and none of their injuries are life-threatening.
Anyone with information on what happened who has not already spoken to police should call the OPP at 1-888-310-1122.
The roadway was reopened a few minutes after 9pm Saturday.