GLENDIVE, Mont. -- The pipeline break that released an estimated 42,000 gallons of crude oil into the Yellowstone River is beneath the river bed, a federal official said Tuesday.

The Pipeline Hazardous Materials Safety Administration confirmed the location of the break, but couldn't say whether the 12-inch diameter Bridger pipeline, which began releasing oil into the river Saturday, lay bare on the river bottom.

Bridger Pipeline spokesman Bill Salvin, said the break was near the south bank of the river. The cause of the break hasn’t been determined.

“We believe the breach is under the riverbed about 50 feet from the south shoreline,” Salvin said. “We are recovering product on the south side, but I don’t know how much.”

In 2011, when an exposed oil pipeline ruptured at the bottom of the Yellowstone River near Laurel, the pipe was assumed to be buried well under the riverbed. It was later determined that an unusually high river flow had scoured several feet of rock cover leaving the pipeline vulnerable.

PHMSA, according to a state pipeline report, inspected Montana’s major pipeline crossings after the Laurel disaster, which spilled 69,000 gallons of oil into the Yellowstone River. While the federal agency required pipeline coverings be fortified at several locations, Bridger Pipelines’ crossing six miles upstream from Glendive was considered sufficiently protected. The depth of the Bridger Pipeline cover was believed to be eight feet in 2011.

But severe flooding and a river-altering ice flow in spring 2014 scoured several miles of the Yellowstone, including the area where the pipeline break occurred.

A 2012 pipeline risk assessment of the site by the Yellowstone River Conservation District found the pipeline at moderate risk because of bank line erosion. The pipeline is downstream from some islands that over several years had altered river flow and increased erosion near the site.

PHMSA could not say Tuesday if anyone had checked to see if the pipeline was still sufficiently buried after the 2012 damage.

Montana Gov. Steve Bullock has declared Dawson and Richland counties a disaster area because of the spill. In an afternoon briefing, the governor said Bridger Pipeline would pay for the cleanup.

“We have expectations that (the company) will provide all the resources necessary,” Bullock said. “My expectation is that they’ll be cleaning this up to our standards.”

Most of the oil is still within six miles of the broken pipeline, Bullock said. Ice covers the river, but where there is open water, crews are using containment booms to control the spread of oil.

“There’s a limited amount of places where the cleanup can be done: Open water, or thick ice, and there’s a lot of places in between,” said Tom Livers, state Department of Environmental Quality deputy director. “They can’t plug the leak, because there is no way to get at it” under the ice.

There is oil sheen on the water as far downstream as Sidney. However, that community relies on well water and hasn’t had the contamination problems that Glendive has.

The Glendive water supply contains the cancer-causing agent benzene, an oil ingredient. Workers are flushing the Glendive drinking-water system, Livers said. The goal is to have all of the volatile organic compounds out of the system by Thursday.

The Billings Gazette is a media partner with Forum News Service.