The main car ferry that crosses Kootenay Lake, B.C., has leaked about 400 litres of gear oil into the lake, leaving a large slick on the water near the dock.
The leak happened at about 9 a.m. PT on Saturday morning.
A manager with Western Pacific Marine, the company that operates the ferry, said the leak was a result of the "catastrophic failure" of one of the Osprey 2000's four propulsion units while the vessel was in transit.
Every measure was made to contain the leak, he said, and the company is still investigating the extent of the damage.
The ferry is expected to be out of service for at least another month, he said.
Interior Health is cautioning people to avoid recreational use along a 400-metre stretch of the shoreline next to the Balfour Ferry Terminal.
The health authority said there doesn't appear to be any drinking water intakes in the area, but people should avoid swimming or letting their pets in the water there.
According to DriveBC, a smaller capacity ferry, the MV Balfour, is still running on its winter schedule.
With files from Bob Keating.