Ontario's Ministry of Natural Resources says a wildfire raging in the northeastern part of the province is only seven kilometres away from a stretch of the Trans Canada highway.
Spokesman Shayne McCool says southwest winds could periodically blow heavy smoke onto Highway 69 and into surrounding communities.
McCool says police are monitoring the situation closely, and if the smoke is heavy enough a portion of the highway could be closed.
The ministry says the fire is now 76 square kilometres, and water bombers are trying to cut it down.
It says the still-growing fire sprung up on July 18, and Ontario firefighters have been backed up by their counterparts from other provinces, the United States and Mexico.
As of Friday night, there were 43 active forest fires across northeast Ontario - 13 of which were out of control.