Provincial police say a pileup involving more than 20 vehicles has shut down the westbound lanes of Highway 401 in Milton.
Ontario Provincial Police Sgt. Kerry Schmidt says at least 15 cars and seven transport trucks are involved in the crash.
He says traffic is backed up for kilometres as a result of the collision and it will take a long time to clear.
Schmidt says some of the trucks involved in the crash are blocking the highway shoulder, which is slowing down access for emergency vehicles and tow trucks.
He says no serious injuries have been reported.
