A locomotive and 10 coal cars plunged about 50 feet early Monday from a track undermined by high water flow on the Yellowstone River.

No injuries were reported, and the unknown amount of coal that spilled into the river was not believed to pose a threat to people or fish.

Engineers with Burlington Northern Sante Fe Railway had been monitoring the area because of high water flows and the train was traveling at a reduced speed when the ground gave way about 1:15 a.m. Monday, company spokesman Gus Melonas said. "We had personnel on the ground observing the train over this area. They could see what happened," he said. "They could see the land give away and the train's 10 cars and locomotive drop" about 50 feet.

The locomotive and a railcar were partially submerged in the river.

The train was en route to Superior, Wis., when it derailment near Forsyth, about 100 miles northeast of Billings.

By Monday evening, crews had pulled all 10 of the cars and the locomotive up the bank. They also had pumped about 2,500 gallons of diesel fuel from the locomotive, which was about one-third submerged, Melonas said.

It was unknown if any fuel spilled into the river, but Melonas said a team would be working with Montana officials to assess possible environmental damage.

Crews were bringing in rock to solidify the rail bed and were building a temporary track around the washout to resume rail traffic. Melonas said they hoped to have the temporary track open as early as Tuesday morning.

The derailment had no effect on passenger traffic, but freight trains were being rerouted.