CHILOQUIN, Ore. (AP) — A wildfire in south-central Oregon is growing rapidly and degrading air quality as it chews through national forestland amid dry, hot and windy conditions.

The fire in Klamath County, which started Tuesday, had grown to nearly 17,000 acres as of Thursday afternoon and was 1% contained, fire authorities said. It was burning in mixed conifer and lodgepole pine in the Fremont-Winema National Forest, 10 miles (16 kilometers) northeast of the unincorporated community of Sprague River.

Temperatures were expected to hit 90 degrees Fahrenheit (32 Celsius) and a red flag warning was in effect in the area. The blaze was on national forestland but residents around Sprague River and Beatty were in a watch zone.

The Oregon State Fire Marshal said the fire was threatening lives, structures, and property as it moved to the south and east Thursday afternoon and that additional resources would arrive Thursday evening to help fight the fire.

The cause of the fire is under investigation.

Farther north, a smaller fire forced multiple service road closures about 40 miles (64 kilometers) east of Roseburg near the community of Steamboat and also caused closures on Oregon Highway 138 due to falling rocks and flames along the roadside as it continued to grow Thursday.

Eagle Rock and Boulder Flat campgrounds are both closed, as is the North Umpqua River to boaters between Boulder Flat downstream to Steamboat Creek.

That fire burning in grass and timber had grown to an estimated 4,224 acres as of Thursday morning and was 0% contained. Mandatory evacuations remain in effect for people living in parts of the unincorporated community of Dry Creek, the Douglas County Sheriff’s Office said.

An air quality advisory is also in effect for Klamath and Lake counties and parts of Douglas and Jackson counties stemming from smoke from both fires. State Department of Environmental Quality officials said Thursday they expect the advisory to be in effect until at least Monday morning.