Flooding waters from the Little Big Horn River have spilled onto Interstate 90 forcing closure of the eastbound lanes, according to the Montana Department of Transportation.
Barricades have been set up and a detour established for eastbound traffic. The westbound lanes were being evaluated, an agency press release states.
The closure was announced shortly before 10 a.m.
BIA officers are on scene. The agency advises to expect delays and to reduce speeds.
The affected area is identified as between mile marker 510 and 515.