Transport Quebec has reopened a stretch of Highway 40 west of Quebec City, closed for more than ten hours after a major pileup involving 27 vehicles Monday morning.

Ministry officials confirmed the westbound lanes of the major artery opened at 8:40 p.m. ET. Earlier, traffic had been diverted onto Highway 138 along the St. Lawrence River.

At least 20 people were hurt in the chain-reaction crash, including one elderly woman whose injuries police describe as serious.

Road conditions remain slippery, and a winter storm warning was still in effect as darkness fell.

Tow trucks haul away wrecked cars, trucks

The accident happened at kilometre 254 of the highway near Saint-Marc-des-Carrières, 70 kilometres west of Quebec City.

Cars and heavy trucks and metal debris were strewn in the ditches on both sides of the highway for several hundred metres.

CBC reporter Ainslie MacLellan spoke to one truck driver, who said he had been driving at about 80 km/h when vehicles directly ahead of his truck began spinning out of control.

He said he swerved into a ditch to avoid the cars in front of him and ended up with the cab of his truck pointing in the opposite direction to the one in which he'd been travelling.

Several of the trucks were carrying heavy loads.

"We know that there [are] no dangerous substances carried by those vehicles," said Quebec provincial police spokeswoman Ann Mathieu. "We'll have to unload them … and eventually, they'll all be towed."

Road conditions slippery

Officials are pointing to winter weather and poor road conditions as the likely cause of the pileup.

"The visibility was good but the surface might have been a little frozen," Mario St-Pierre of Transport Quebec said.