MORGANTON, N.C. -- Firefighters are making progress in controlling a wildfire in Pisgah National Forest in Burke County, although the blaze has grown to 1,800 acres.

Officials hope that rain forecast for Sunday and Monday will help bring the fire under control.

Deborah Walker of the U.S. Forest Service said authorities used “burn-out tactics” Thursday. That involves establishing containment lines in the ground, then starting a fire moving toward the active fire. Walker said the new fire creates a barrier that the active fire cannot pass because the burned out areas remove fuels.

No homes are threatened. Crews are protecting two dozen structures at the Outward Bound complex.

There have been no injuries. The cause of the fire is unknown.

Some trails in the area have been closed because of the fire.

State officials have issued an air pollution advisory for the western Piedmont region because of the wildfire.

The N.C. Division of Air Quality issued the advisory for Burke, Caldwell and McDowell counties, where residents could experience unhealthy air quality, depending on wind directions.

The 1,800-acre wildfire is centered in the Linville Gorge Wilderness near Table Rock Mountain, and satellite photos show a large plume of smoke drifting downwind. Smoke could reach as far as Marion and Hickory, and officials say heavy smoke from the fire could contain high levels of particle pollution.

Residents could experience Code Orange conditions Friday in the three counties. Parts of Wilkes, Surry, and Alexander counties may also see some heavier smoke, depending on the fire’s growth and intensity.