An avalanche Saturday night closed Idaho 21 between the Grandjean Junction and Banner Summit, the Idaho Transportation Department said.
The avalanche occurred Saturday night at about 5 p.m. 20 miles east of Lowman. The slide was caused when wet, heavy snow created unstable snow conditions along the steep canyon walls.
Six vehicles were blocked by the slide but evacuated by a transportation department snow plow. Signs advising motorists of the closure are posted outside of Boise, Banks, Idaho City, Stanley and Lowman.
Transportation department officials estimate the highway will remain closed until Tuesday or Wednesday.
Motorists need to travel to Stanley during the idaho 21 closure should use U.S. 20 and Idaho 75.