A stretch of Highway 401 east of Oshawa, Ont., reopened late Friday night after a massive pileup involving as many as 80 vehicles closed down the busy artery for several hours.

Eastbound lanes were cleared by 10:30 p.m. ET, while westbound lanes reopened at 11:40 p.m. ET, according to Ontario Provincial Police.

It appears the worst part of the pileup was near Newcastle, at the Highway 35/115 exit.

"It just never ends. We stopped counting at 70 cars," said Filippo Fazzino, who was driving on the highway when the pileup happened.

Cars and trucks litter a 1.5 kilometre area of the highway. (Canadian Press )

Crumpled, twisted wrecks were strewn along a 1.5-kilometre stretch of Canada's busiest highway. Police had to reroute traffic around the accident scene.

The EMS chief for Durham Region said Friday afternoon that five people had been taken to hospital. That was later confirmed by OPP spokesperson Const. Linda Wolf.

Two of the patients had life-threatening injuries. The other three had injuries which Wolf described as "non-life-threatening."

Weather conditions were far from ideal at around 3 p.m. ET when the accident happened. Snow squalls from Lake Ontario hit the highway and undoubtedly played a role in the accidents.

"It's too early to say what was the cause of the collision. We definitely will be looking at the weather conditions. We do have unfavourable driving conditions right across the Greater Toronto Area right now, so it's a wonderful opportunity to remind everybody to turn your headlights on, slow down, be aware of your stopping distances."

Medical responders said they were amazed, considering number of car, trucks and transports involved that there was "more wreckage than injuries."