The eastbound lanes of Highway 401 near Woodstock, Ont., have reopened following a massive pileup involving at least 50 vehicles on Friday afternoon.

An approximately 10-kilometre-long stretch of highway — between Foldens Line and Mill Street — was closed earlier in the day during the investigation and cleanup of the crash that occurred just before 1 p.m. during a snow squall.

Video from the crash scene showed jackknifed tractor-trailers and other smashed vehicles scattered amid the snowy conditions.

A 10-kilometre-long stretch of Highway 401 near Woodstock, Ont., has reopened following a 50-car pileup. (Jennifer McGuire/CBC)

Const. Lisa Narancsik said several motorists had minor injuries.

The Ontario Provincial Police's Greater Toronto Area traffic Twitter account posted a message saying that Highway 401 westbound at Drumbo Road had also closed temporarily during severe weather conditions.

A week ago a stretch of Highway 401 east of Oshawa was closed for several hours after an 80-vehicle pileup that occurred during a snow squall.

CBC meteorologist Johanna Wagstaffe notes that snow squalls and whiteout conditions can occur unpredictably in narrow bands with little warning, especially on open highways without trees or fences to shield from the wind. After a warm summer and mostly mild winter, the lower Great Lakes are open and a couple of degrees warmer than usual.

"You get the westerly winds that are much colder, greater than 15 degrees colder than the water, picking up all that moisture and depositing on the lee shores. We’ll be watching for snow squalls in the next couple of weeks."