Associated Press

HELENA, Mont. - An inversion holding heavy smoke over western Montana is robbing wildfires of oxygen and preventing the sun from heating up ground fuels, helping firefighters make progress, fire officials said.

Residents near Essex remain under an evacuation advisory as a blaze that has burned just under a square mile remains about a mile from the town on the southern edge of Glacier National Park.

U.S. Highway 2 remains open with pilot cars, and the rail line through the area is also open as crews work to keep the blaze away from Essex and the transportation corridor.

Crews planned to do burnout work Tuesday on fires near Noxon in northwestern Montana and Clark Fork in northern Idaho. They won't have to worry as much about the fires taking off because of the smoke, but it hampers air support for firefighters.

The Department of Environmental Quality is reporting very unhealthy air quality in St. Mary and the Flathead Valley along with Frenchtown, Missoula and Hamilton. The air quality in the Libby area is hazardous.