LAUREL, Montana - Authorities struggled Sunday to gauge the environmental and crop damage from tens of thousands of gallons (liters) of oil that spilled into the legendary Yellowstone River, as Montana's governor criticized Exxon Mobil for downplaying the scope of the disaster.

A break in a company pipeline near Laurel fouled miles (kilometers) of riverbank and forced municipalities and irrigation districts to close intakes across eastern Montana.

Exxon Mobil brought in more cleanup workers to mop up crude at three sites along the flooded river that were coated with thick globs of crude. Yet there was no clear word on how far the damage extended along a scenic river famous for its fishing and vital to farmers who depend on its water for their crops.

The uncertainty frustrated riverfront property owners such as Linda Corbin, who worried that severe damage would be revealed as the flooding Yellowstone recedes in coming weeks. The stench of spilled crude was obvious in Corbin's backyard - a reminder of the potential problems lurking beneath the surface of the nearby river. ' Schweitzer said. "The Yellowstone River is important to us. We've got to have a physical inspection of that river in small boats - and soon."

Exxon estimated that up to 1,000 barrels, or 42,000 gallons (159,000 liters), spilled Saturday before the flow from the damaged pipeline was stopped. An EPA representative said only a small fraction of the spilled oil was likely to be recovered.

State officials earlier reported a 25-mile (40-kilometer) long slick headed downstream toward the Yellowstone's confluence with the Missouri River, just across the Montana border in North Dakota. Authorities had no further reports on that slick, and Pruessing said the oil appeared to be evaporating and dissipating as the Yellowstone carries it downstream.

Pruessing also said that the pipeline had been temporarily shut down in May because of concerns over the rising waters on the Yellowstone. He said the company decided to restart the line after examining its safety record and deciding the risk was low.

The US Department of Transportation, which oversees pipelines, last year issued a warning letter to Exxon Mobil that cited seven safety violations along the ruptured Silvertip pipeline. Two of the warnings faulted the company for its emergency response and pipeline corrosion training.

Transportation department spokeswoman Patricia Klinger said the company has since responded to the warnings and the case was closed.

The company and government officials have speculated that high waters in recent weeks may have scoured the river bottom and exposed the pipeline to debris that could have damaged the essure readings dropped early Saturday. Pruessing said workers began shutting down the line within six minutes, although company officials declined to say how long that process took.

The spill was small compared to other oil-related disasters, such as the 11 million gallons (41.64 million liters) leaked by the Exxon Valdez in Alaska in 1989. But officials said the pristine nature of the Yellowstone, along with its turbulent waters and riverside communities, complicated their cleanup efforts and attempts to assess the damage.