Ontario Provincial Police have closed a portion of Highway 400 in Barrie following multiple collisions due to whiteout conditions.

The highway is closed between Mapleview Drive and Highway 89.

"Multiple collisions in the area; near zero visibility; blowing snow; lots of wind; dangerous conditions here. Crashes are happening all up and down that area. If you don't need to be on the roads, please stay off the highway," OPP Sgt. Kerry Schmidt said in a video posted to Twitter.

It is not immediately known how many crashes have occurred, and there is no word on injuries.

A snow squall warning is in effect in Barrie.

"Snow squalls off Georgian Bay will continue to affect portions of the region through this evening. Heavy snow combined with northwesterly winds gusting 50 to 70 km/h could produce near-zero visibility at times," Environment Canada said in its advisory.

The agency said the area could see 15 to 25 centimetres of snow. Conditions are expected to improve in the evening as snow and winds taper off.