An estimate on the fire size late Monday was about half what it was at the beginning of the day, thanks to aerial mapping.
One mobile home has already burned in the fire, although authorities say the person living in the home was safely evacuated and no other injuries have been reported.
The North Schell Fire is burning steep, rugged terrain on the east side of the Schell Mountain Range, about 20 miles north of Ely. It started June 9 as a prescribed burn by the Forest Service.
Authorities say their priority is protecting people, private property and sage grouse and mule deer habitats.