The cleanup from a massive 50-vehicle pileup on Highway 401 near Trenton, Ont., may not be completed until sometime on Thursday.

Traffic on the westbound lanes reopened several hours after the pileup, but by Wednesday night the eastbound lanes remained closed between County Road 30 and County Road 40.

Ontario Provincial Police Sgt. Kerry Schmidt told CBC Radio's Here and Now Wednesday afternoon that drivers heading east through the area should anticipate delays.

"People need to plan alternates and just plan for longer travel times through that area," he said in a telephone interview just after 5 p.m. on Wednesday afternoon.

Schmidt said the eastbound side of the highway is not expected to reopen until the overnight hours at the earliest.

"It is unfortunately going to be a long-term closure here while the cleanup continues," Schmidt said.

Weather to blame, police say

The OPP blamed the crash on poor weather and said it happened in the eastbound lanes of the highway around 12:08 a.m. One tanker truck spilled 40,000 litres of oil.

Police said four people were injured in the pileup, but their injuries are considered non-life-threatening.

Truck driver James Dawson, who managed to bring his vehicle to a safe stop amid the chaos, said the pileup happened on a downhill stretch of highway that was covered in hard-packed snow as slick as ice. Making matters worse, a sudden snowfall created blizzard-like conditions.

"It's a mess down here," Dawson told CBC News on Wednesday morning.

Dawson said he's seen plenty of accidents on the 401 — which truckers call "the corridor" — but nothing like this.

"It's crazy," he said, adding he's amazed nobody was killed.

He said he counted 33 tractor-trailers that were damaged in the mass collision, including an oil tanker tipped on its side. The damage varies, but it appears some trucks may be total writeoffs.

"Trailers are chopped in half," he said.

More than 50 people involved in the collision were taken to a nearby hotel to spend the night.