A bridge that crosses Yellowstone River in Montana has collapsed, causing parts of a freight train carrying hazardous materials to plunge into the flooded river below.

The train’s carriages were carrying asphalt and sulphur, said David Stamey, Stillwater County’s chief of emergency services.

Officials shut down drinking water intakes downstream while they evaluated the danger.

An Associated Press reporter witnessed a yellow liquid pouring out of tankers but Mr Stamey said there was no immediate danger for the crews working at the site, and the hazardous material was being diluted by the swollen river.

Montana Bridge Collapse
Kelly Hitchcock closes an irrigation ditch just down river from a bridge collapse (Matthew Brown/AP)

The train crew was safe and no injuries were reported after the bridge collapse, according to a statement from Andy Garland, spokesman for the Montana Rail Link.

Mr Garland said “several” tankers were partially submerged in the river early on Saturday, and crews were at the scene in Stillwater County, near the town of Columbus, about 40 miles west of Billings.

“We are committed to addressing any potential impacts to the area as a result of this incident and working to understand the reasons behind the accident,” Mr Garland said.

In neighbouring Yellowstone County, officials said they instituted emergency measures at water treatment plants due to the “potential hazmat spill” and asked residents to conserve water.

The cause of the collapse is under investigation, he said.

APTOPIX Montana Bridge Collapse
The cause of the collapse is under investigation (Matthew Brown/PA)

The site is in a sparsely populated area in the Yellowstone River Valley, about 110 miles north east of Yellowstone National Park.

The Montana Disaster Emergency Services has been notified. Federal Railroad Administrators officials were at the scene.

The river was swollen with recent heavy rains although it is unclear whether that contributed to the bridge collapse.

Kelly Hitchcock, of the Columbus Water Users, shut off the flow of river water into an irrigation ditch downstream from the collapsed bridge to prevent contents from the tankers reaching nearby farmland.

The Yellowstone saw record flooding in 2022 that caused extensive damage to Yellowstone National Park and adjacent towns in Montana.

The US Environmental Protection Agency notes that sulphur is a common element used as a fertiliser as well as an insecticide, fungicide and rodenticide.