An oil train derailed Thursday in rural northeastern Montana, prompting the evacuation of some homes and leaving at least two of the cars leaking crude, authorities said.

There were no immediate reports of injury or fire, but of the 21 cars that derailed only two remained upright, Roosevelt County Sheriff Jason Frederick said.

Burlington Northern Santa Fe spokesman Michael Trevino said the train was pulling 106 loaded crude oil cars when it derailed near Culbertson near the North Dakota border just after 6 p.m. MDT.

Police, fire and other emergency responders were at the site of the derailment, which forced the closure of federal Highway 2, the region's main artery.

Frederick told The Associated Press that crews are not going too close to the leaking cars until a BNSF hazardous materials team, enroute from Texas, reaches the scene.

But he said that there was no immediate threat to public safety.

The sheriff didn't know how many homes were evacuated but described area as a rural setting with ranch homes spread apart.

The Billing Gazette reported that the derailment came only about six hours after traffic started moving again after another BNSF derailment further west near Fort Kipp on Tuesday.

Rail officials declined to specify if the train was hauling crude from North Dakota's Bakken oil patch, where growing numbers of shipments that have increasingly drawn safety concerns.

Trains hauling crude from the Bakken region have been involved in multiple derailments in recent years, some causing fires.

U.S. transportation officials recently extended an order for railroads to notify states about shipments of hazardous crude oil shipments.