As many as six small avalanches forced the Montana Department of Transportation to close all eastbound and westbound lanes of Interstate 90 from St. Regis to Lookout Pass at the Idaho border.
DOT officials say crews cleared the slides, but the road will be closed all night as the threat of a larger slide looms.
Steve Felix, The maintenance director for the Department of Transportation, says blasting will occur in the area Tuesday morning to reduce the danger.
Traffic is being diverted from St. Regis up highway 200 through Sand Point, Idaho. Local residents are still allowed to travel on I-90 to Saltese.