An empty Montana Rail Link coal train heading east near Clinton ran into a steel culvert filled with rocks Thursday evening.
The train engineer told investigators it looked like a large trash can on the track.
The Missoula County Sheriff's Department said the impact cracked a window on the train. There were no injuries.
Investigators found mangled pieces of culvert and rocks scattered around.
They also found a shovel and a large hole dug into the side of a berm about 30 yards away.
The hole was concealed with sticks.
Investigators said from photographs it looks like someone could have hidden inside the makeshift cave.
Montana Rail Link told NBC Montana there have been similar incidents within this 1-mile radius in the past three weeks.