The Horseshoe Fire, which is burning 10 miles southwest of Polson, has now scorched an estimated 140 acres and is 20 percent contained.
The blaze -- which fire officials report was sparked by an unattended campfire -- is burning in a Ponderosa pine and juniper stands along the banks of the Flathead River.
There are 49 personnel assigned to the fire, according to the CSKT Division Fire.
Fire managers report that active interior fire behavior with single tree torching was observed on Thursday and helicopters performed bucket work on hotspots.
There are no evacuations and no structures threatened at this time.