Officials closed a portion of State Highway 21 in both directions in southwest Idaho on Tuesday due to a 7-square-mile wildfire burning trees, brush and grass in rugged terrain.
Fire managers gave no timeline for when the highway might reopen as some 850 firefighters backed by aircraft work on fire lines to contain the blaze that started July 18.
The highway is closed from east of Idaho City to north of Lowman as firefighters prep the area for defensive operations.
The highway is a well-traveled route from highly populated southwest Idaho to vacation areas in central Idaho.
The fire burning about 8 miles north of Idaho City is 32 percent contained.
Officials say no structures have been destroyed. The cause of the fire is unknown.