BRIDGER, Montana (AP) — An evacuation warning was issued for residents near the small town of Bridger in south-central Montana after a train derailed and two fuel cars ruptured and leaked an estimated 31,000 gallons of gasoline, authorities said Saturday.

BNSF Railway Co. said there were no injuries, and crews were working with local officials and hazardousmaterials responders to safely clear the site.

The derailment of the southbound train occurred on a curving portion of the track about half a mile east of the small town of Bridger, population of about 660. The town is about 45 miles southwest of Billings.

"Two of the derailed cars were compromised and leaked gasoline," said BNSF spokesman Ben Wilemon in an email to The Associated Press. "The cause of the derailment is under investigation."

A 30,000-gallon tank emptied completely and a second damaged tank leaked about 1,000 gallons before BNSF workers repaired the tank, The Billings Gazette reported. There was no immediate information on whether the spill contaminated groundwater or the area's irrigation systems.

Authorities said that about 15 cars derailed not long after midnight local time. Four of the derailed cars contained petroleum. Officials said the train had more than 100 cars, and it was also moving coal, sorghum and particle board.

The tracks in that area in some portions run near the meandering Clark's Fork of the Yellowstone River.

Maggie Karas, Carbon County Disaster and Emergency Services spokeswoman, said the river wasn't affected.

Emergency responders from multiple agencies initially responded to the scene. Heavy equipment has been brought in to clear the tracks. Cars that stayed on the tracks were being moved north Saturday afternoon away from the derailment.

Officials have closed several roads in the sparsely populated area north of the Wyoming border and are asking people to stay away.

"We just ask the public to avoid the area to allow workers to safely mitigate the situation," Karas said.