A busy stretch of Highway 400 south of Barrie has reopened after a 96-vehicle pileup during a whiteout Thursday morning.

Ontario Provincial Police Sgt. Dave Woodford said the collisions happened at about 9 a.m. as a sudden snow squall swept over the highway, reducing visibility to "a few feet."

"It could have been a lot worse," said Woodford. "People were slowing down."

The pileup led to the closure of Highway 400 between Highway 89 and Mapleview Drive. Both lanes on that stretch of Highway 400 remained closed to traffic for most of the day until early evening.

The highway's reopening was delayed because a truck sent to repair a broken guardrail crashed en route to the scene.

Environment Canada warned that blowing snow would be a problem for drivers in the Barrie area on Thursday. This image was taken near Bradford, Ont., from a vantage point on Highway 27, which was jammed as a result of the shutdown of Highway 400. (Shannon Martin/CBC)

A special weather statement from Environment Canada warned that blowing snow would be a hazard for drivers in the region.

While no major injuries were reported from the pileup, the ensuing cleanup is a major task for police.

Police set up a collision centre at Georgian Downs racetrack, which is located off the highway near the crash site.

"There was an army of tow trucks at the scene," said Woodford.

Data on the Ontario Ministry of Transportation website suggests that more than 80,000 vehicles travel along the affected stretch of highway each day.

As a result of the shutdown, traffic was heavy along Highway 27, which lies to the west of Highway 400.

When a snow squall hits, what should drivers do?

Woodford said drivers caught in a snow squall should slow down and keep their headlights on to improve visibility for other drivers. He said some drivers are inclined to pull over, but he said it's better to keep the car moving slowly.

"Just crawl through it," Woodford told CBC News. "Snow squalls come in quickly but they leave quickly too."