An unmanned 107-car freight train broke loose at Garrison Monday night and was intentionally derailed east of Clinton without injury, Montana Rail Link said.
The eastbound train was traveling backward when it was derailed in an area of sparse population and as far from the Clark Fork River as possible, officials said.
Traffic on nearby Interstate 90 was stopped temporarily, power was knocked out in the area, and scores of people were alerted but not evacuated.
State officials said none of the 47 derailed cars released any hazardous material. Many were loaded with lumber and paper products.
“I-90 was closed for precautionary purposes until the site has been declared safe,” officials said.
Traffic resumed about 9 p.m. The derailment occurred shortly before 7 p.m.
Montana Power Co. said a 100,000-volt transmission line was knocked out at 6:58 p.m., disrupting power to Drummond, Philipsburg, Georgetown Lake and surrounding areas. Power was restored at 7:21 p.m., said spokesman Cort Freeman.
Two of the derailed cars were empty but contained residual hazardous materials - distilled alcohol and gasoline - although none escaped, said the Disaster & Emergency Services Division in Helena.
Circumstances of how the train broke loose were unclear, but train crews are frequently changed at Garrison.
From Garrison, the eastbound train traveled 46 miles backward before it was derailed at Bonita, eight miles east of Clinton, officials said.
“The intentional derailment was done at an unoccupied area when it was determined that there were no loaded hazardous materials on the train,” the state agency said.
Paul Laisy, operations chief for the Missoula County Rural Fire Department and the incident information officer, said authorities went door-to-door for a radius of 2 miles alerting people about a possible evacuation, but it wasn’t necessary.
Special teams dispatched to handle hazardous materials were recalled about 9:15 p.m.
Dan Watts, MRL’s vice president of operations, said the eastbound train had stopped at Garrison to add an engine unit. The crew was off the train when it began rolling backward, he said.
“MRL has never had this happen before,” Watts said during a news conference.