The authorities said an investigation was continuing but that “it is believed that extremely icy road conditions” caused the bus to roll over. 

Four people were killed and dozens of others were injured after a bus rolled over on an “extremely icy” highway in British Columbia on Christmas Eve, the authorities said.

The Royal Canadian Mounted Police said the bus crashed around 6 p.m. local time on Highway 97C east of Merritt, about 170 miles northeast of Vancouver.

The identities of the four people killed were not released and details about where the bus was traveling from, where it was headed and who owned it were not immediately available.

Emergency responders transported 52 people to hospitals. Of those, 36 chose to be treated for injuries that ranged from minor to serious, according to Michaela Swan, a spokeswoman for the health care provider Interior Health.

Of those who remained hospitalized as of Sunday, two were in serious condition and two had injuries that were not life-threatening, she said.

“Although the number of patients remaining in hospital is low, this is a life-altering incident for all involved, from the initial physical injuries to the emotional and spiritual impacts,” Ms. Swan said in a statement.

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The R.C.M.P. said an investigation into the crash was ongoing but that “it is believed that extremely icy road conditions caused the rollover.” The temperature was about 21 degrees Fahrenheit (minus 6 Celsius) in Merritt around the time of the crash, according to weather records.

In a statement, the premier of British Columbia, David Eby, and government ministers said they were “shocked and saddened” to hear of the crash.