Montana Rail Link has begun cleaning up a derailment that occurred Saturday morning on a bridge near Reed Point, southeast of Big Timber, sending rail cars loaded with molten sulfur and asphalt into the Yellowstone River. The derailment occurred at approximately 6:45 a.m. Saturday, when a westbound train traveling from Laurel to Missoula derailed while crossing the river. Nobody was injured in the wreck. The cause of the derailment is under investigation, and it’s currently unclear whether a bridge collapse caused the derailment, or a derailment caused the bridge to collapse.