Twenty-five vehicles were involved in several chain-reaction crashes that closed the southbound lanes of Highway 400 near Highway 88 for several hours.
Ontario Provincial Police say the weather was clear and at the time, and it appears drivers were just travelling too fast.
Police believe the first crash occurred just before noon when a driver lost control and collided with several other vehicles. The accident blocked several lanes, causing traffic to slow.
Approaching vehicles couldn't stop in time, and several slammed into the slowed cars, police said.
Several tractor-trailers were involved, including some that ended up in the ditch, Const. Dave Woodford told CTV.ca from the scene. Several vehicles collided with one stopped truck, which caused it to jackknife.
There were other single-vehicle collisions, where cars spun out and hit the guardrail or ended up in the ditch.
There were no reports of serious injuries, Woodford said.
The tie-up triggered a significant traffic backlog. The area reopened at about 3 p.m.
Sections of highways around the Toronto area, as well as main roads and side streets, were still slippery on Monday following the massive storm that dumped between 25 and 30 centimetres of snow in most areas on Sunday.
