Hundreds of barrels of crude oil spilled into Montana's Yellowstone River after an ExxonMobil pipeline beneath the riverbed ruptured.

The plume travelled 25 miles downstream and forced temporary evacuations, officials said.

The break near Billings in south-central Montana fouled the riverbank and forced municipalities and irrigation districts Saturday to close intakes.

Pollution: Oil swirls in a flooded gravel pit in Lockwood, Montana after a pipeline break yesterday

The river has no dams on its way to its confluence with the Missouri River just across the Montana border in North Dakota. It's not known how far down the river the plume may travel.

Cleanup crews deployed booms and absorbent material in a race to mop up the oil as the plume sailed downstream at up to seven miles an hour.

'The parties responsible will restore the Yellowstone River,' Montana Gov. Brian Schweitzer vowed.

A 600-foot-long black smear of oil coated Jim Swanson's riverfront property just downstream from where the pipe broke.

'Whosever pipeline it is better be knocking on my door soon and explaining how they're going to clean it up,' Swanson said as globules of oil bubbled to the surface.

Blackened: Up to 1,000 barrels of oil are said to have spilled into the Yellowstone River, sending a plume 25 miles downstream

'They say they've got it capped off. I'm not so sure.'

ExxonMobil spokeswoman Pam Malek said the pipe leaked an estimated 750 to 1,000 barrels of oil for about a half-hour before it was shut down.

Other Exxon officials had estimated up to 42,000 gallons of crude oil escaped.

Duane Winslow, Yellowstone County director of disaster and emergency services, said the plume was dissipating as it moved downstream.

'We're just kind of waiting for it to move on down while Exxon is trying to figure out how to corral this monster,' Winslow said.

Emergency: Residents have been evacuated from their homes close to the leak in the Montana river

'The timing couldn't be worse,' said Steve Knecht, chief of operations for Montana Disaster and Emergency Services, who added that the plume was measured at 25 miles near Pompeys Pillar National Monument.

'With the Yellowstone running at flood stage and all the debris, it makes it dang tough to get out there to do anything.'

Brent Peters, the fire chief for the city of Laurel about 12 miles west of Billings, said the rupture in the 12-inch diameter pipe occurred late Friday about a mile south of Laurel.

He said about 140 people in the Laurel area were evacuated early Saturday due to concerns about possible explosions and the overpowering fumes.

Disaster: An Exxon spokesman said the company regrets the disaster

He said they were allowed to return at about 4 a.m. after fumes had decreased.

Two teams of emergency workers are taking part in the clean-up operation along the river and an additional 100 contractors are expected to arrive from Washington to help in the effort.

Glenn Wells said he and his wife were asked to evacuate their home at 2:30 am.

'I still smell like oil,' he said. 'My whole house smells like diesel fuel. It was everywhere on the river - an oil slick on Billings' West End.'

'The river will never be the same,' he told the Billings Gazette.

A spokesman for ExxonMobil said: 'We regret the release.'