Icy roads are being blamed for several crashes that occurred on a major Ontario highway after freezing rain swept through the Barrie region early Friday morning.

After a spate of collisions, Ontario Provincial Police were forced to shut down a 12-kilometre stretch of Highway 400, south of Barrie, shortly after a flash freeze at about 4 a.m. The lanes were closed for almost six hours.

At least four crashes were reported, including one that sent a woman to hospital with life-threatening injuries, said OPP spokesman Sgt. Dave Woodford.

In that crash, a car flipped onto its roof.

In another crash, a tractor-trailer that was hauling a load of non-hazardous goods jackknifed and slid into a ditch.

Because of dangerous conditions on roads, ramps and bridges, OPP urged motorists to drive with "extreme caution."

In these conditions, Woodford said, people should slow down, take their time and stay focused on the road.

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