Crews are still cleaning up after 45 empty coal cars went off the track near Olney.
No one was hurt, but the derailment closed part of US Highway 93.
The train was heading east from British Columbia.
Some of the cars fell off a bridge over the highway.
Amtrak's Empire Builder uses these same tracks. Some of those trains will have to wait in Spokane and Whitefish until the tracks are cleared.
Officials hope to open the road and tracks again before Monday.