Four people have died and dozens more were injured after a passenger bus rolled over in western Canada, with authorities saying Sunday that icy roads were likely the cause.

The accident occurred Saturday evening on a highway some 330 kilometers (200 miles) east of Vancouver in an area of British Columbia hit by days of bad winter weather.

Federal police said Sunday afternoon they suspected "extremely icy road conditions" caused the rollover, but that the investigation was ongoing.

"Four people are confirmed deceased and multiple people have sustained injuries," the police statement added.

The regional health authority said that fifty-three people in total had been treated at hospitals after the accident, with 36 having "serious to minor" injuries.

As of Sunday morning, eight people were still hospitalized, including two in critical condition.

British Columbia Premier David Eby said he was "shocked and saddened" by the news.

"Our thoughts are with those impacted by the crash, their loved ones, and the first responders and health-care workers giving their all to treat people and keep them safe," he said in a statement.

A portion of the highway impacted by the crash was closed into Sunday morning, provincial transportation authorities tweeted.

The accident occurred as brutal weather has battered wide swathes of North America, snarling transport and causing numerous deadly accidents during one of the busiest travel periods of the year ahead of Christmas and New Year holidays.

On the other side of Canada, trains between Ottawa and Toronto were disrupted throughout the day on Saturday and Sunday due to downed trees and power outages caused by a massive winter storm.

"To Canadians affected by winter weather across the country — please stay safe," tweeted Prime Minister Justin Trudeau on Saturday.

"Crews are working hard to clear roads, restore power, and bring services back online. Let's check in on our friends and neighbours to ask how they're doing and see if they need anything," he added.