LAUREL, Mont. – Authorities struggled Sunday to gauge the environmental and crop damage from tens of thousands of gallons 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 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 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.

“The smell has been enough to gag a maggot,” said Corbin, 64. “I just hope it doesn’t come too far because I’m on a well, and I won’t appreciate having to shower in Exxon oil.”

Environmental Protection Agency spokeswoman Sonya Pennock said its staff had spotted oil at least 40 miles downstream. There were other reports of oil as far as 100 miles away, near the town of Hysham.

After Exxon Mobil Pipeline Co. President Gary Pruessing said flyovers had shown most of the damage was limited to a 10-mile stretch of river, Democratic Gov. Brian Schweitzer dismissed the claim as premature.

Schweitzer said Exxon Mobil needed to get more personnel to inspect the situation close-up. He also slammed Pruessing’s statement to reporters that no injured wildlife had been found.

“For somebody to say at this early stage that there’s no damage to wildlife, that’s pretty silly,” 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, spilled before the flow was stopped. An EPA representative said only a fraction of the spilled oil was likely to be recovered.

State officials earlier reported a 25-mile-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.