Local media outlet KPAX quoted MLR spokeswoman Lynda Frost, who said an incident involving a large obstruction on the tracks occurred about 8.40pm Thursday night near Clinton, Missoula County, with one of its westbound trains.

Missoula County sheriff detective lieutenant Scott Newell told the station the obstacle turned out to be a steel pipe filled with rocks. It measured about 1.8m long and was laid across the tracks.

The coal train, which was empty at the time, reportedly struck the pipe while traveling about 90 kilometres per hour.

“The act of violence resulted in damage to the locomotive, but thankfully no crew were injured,” Frost said, adding it was one of several similar attempts made in the area in the past few weeks.

Newell added that a hole was dug into a nearby hillside, perhaps to allow the guilty party to view the train’s potential derailment.

Authorities are seeking more information on the incident from the public, and Crimestoppers has offered a cash reward for more information.

Officials did not say whether the recent rash of sabotage attempts were related to heightened levels of controversy in Montana and other Pacific Northwest states over planned export coal facilities, some of which are in public comment periods.