Montana Train Derailment Sends Freight Cars Into Yellowstone River

Ten cars from a freight train plunged into the Yellowstone River in Montana on Saturday after a derailment and a bridge collapse, causing asphalt and molten sulfur cargo to spill into the water, the authorities said.

The Montana Department of Environmental Quality tested the water along waterways and treatment facilities in Yellowstone and Stillwater Counties on Sunday and “found no negative impacts,” said David Stamey, the chief of emergency services in Stillwater County.

Officials were investigating whether the derailment or the bridge collapse happened first, as well as how much of the cargo had spread into the river.

What led up to the derailment was not immediately known, officials said.

The train cars, operated by Montana Rail Link, derailed around 6:45 a.m. local time as they headed west in Stillwater County, the county’s Disaster and Emergency Services Department said on Facebook.

State officials and Montana Rail Link on Sunday were coordinating cleanup efforts, Mr. Stamey said.

Andy Garland, a Montana Rail Link spokesman, said no one was injured. Mr. Garland said that two other cars were carrying sodium hydrosulfide but neither landed in the water or been breached.

Wendy Buckley, the president and chief executive of STARS HazMat Consulting, a firm that serves manufacturers, distributors and carriers of hazardous materials, said that the primary hazard from hot asphalt and molten sulfur was their high temperatures.

When hot sulfur mixes with water, it can create sulfuric acid, which can kill fish, Ms. Buckley said. But if sulfuric acid was created, it would be “extremely diluted being that it’s in a river,” so the long-term effects would be “very minimal,” she said.

If the asphalt, a petroleum product, was in a very liquid state when it breached, it would be more likely to spread and affect the river, Ms. Buckley said. Officials said that the material was moving slowly, so the environmental effects would likely also be minimal, she said.

“This stuff is only hazardous because it’s really hot,” Ms. Buckley said, adding, “This is not ideal by any means, but it is not a crisis either.”

The derailment happened between Reed Point and Columbus, in an area about an hour west of Billings.

Video of the scene showed the collapsed bridge with rail cars peeking above the flowing water. It was not immediately clear when the bridge was constructed or when it was last inspected.

Mr. Garland said Montana Rail Link was “committed to addressing any potential impacts to the area as a result of this incident and working to understand the reasons behind the accident.”

The derailment in Montana came about four months after a train carrying toxic chemicals derailed in eastern Ohio, igniting a fire that covered the town of East Palestine in smoke. That derailment prompted concerns about residents’ health and the environment.