Canadian military aircraft helped on Tuesday to rescue hundreds of motorists stranded by an unusually fierce winter storm that closed a key transport link in southwestern Ontario.

By Tuesday afternoon, police had reached most of the more than 300 people who were stranded, some overnight on Monday, in cars and trucks on Highway 402 near Sarnia, Ontario. The storm had been too severe for snowplow crews to keep the road open.

"We're making great progress," said Ontario Provincial Police Sgt. David Rektor.

A local state of emergency was declared in the area about 70 miles northeast of Detroit, Michigan.

"We're talking violent winds and heavy snow ... Some of these cars are stuck in drifts that are four or five feet deep," Rektor said

Dangerous weather conditions with accumulating snow and a wind-chill factor that make temperature feel like -20C (-4F) were expected to last into Wednesday in some areas near Sarnia, according to Environment Canada forecasters.

No injuries or deaths were reported.

General Motors idled its Oshawa, Ontario, assembly plant as the storm cut its supply of parts. A second GM plant, in Ingersoll, Ontario, was working on partial shifts.

Ford Motor Co said it expects the storm will disrupt production at its Canadian assembly plants, although Chrysler said it did not expect to experience problems.

Canadian National Railway said its rail line through Sarnia remained open, although the weather was slowing operations.

A military airplane and at least two helicopters equipped with rescue equipment were being used to assist ground crews as they tried to reach stranded cars, Defense Minister Peter MacKay told reporters in Ottawa.

The helicopters and ground crews helped people get to emergency shelters to warm up. Drivers that decided to stay with their vehicles were given advice on how to remain safe, officials said.