Tens of thousands of gallons of crude oil has spread across Montana's famous waterway.

THE GIST

A pipeline rupture Friday night released an estimated 1,000 barrels, or 42,000 gallons of oil.

Fast flows and floodwaters along the river have spread the oil slick 100 miles from the source of the spill.

The spread of an estimated 1,000 barrels or 42,000 gallons of crude oil along the flooded banks of the Yellowstone River in Montana is becoming increasingly difficult to capture since an ExxonMobile pipeline ruptured late Friday night.

The break in the pipe near Laurel, Mont., forced an immediate evacuation of about 140 people from the town to protect them from possible explosions and dangerous fumes.

Brent Peters, the fire chief for Laurel, told the Associated Press that once the leak was detected he asked the three oil companies with pipelines in the area to shut down their flows. The residents were allowed to return to their homes around 4 a.m. on Saturday. ExxonMobile reports that pipeline pumps were shut down seven minutes after the loss of pressure in the system.

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While the fumes have dissipated to safer levels, the smell of the oil still permeates the air downstream and 12 miles to the east through the city of Billings, where the oil pipeline terminates. ExxonMobile, Cenex Harvest Refinery and Conoco Phillips all have refineries in Billings. The 12-inch diameter ExxonMobile pipe that ruptured was buried six feet below the riverbed and carrying crude oil from Belfry, Mont.

ExxonMobile clean-up crews from the Billings refinery laid out absorbent material and booms along the banks and across the Yellowstone River on Saturday, but the fast flows and flooding has hampered efforts to contain the spread. ExxonMobile sent a team of 50 more oil spill responders to the area on Sunday.

The Environmental Protection Agency, the Montana Department of Environmental Quality, Montana Fish, Wildlife and Parks, and the International Bird Rescue as well as local and state authorities are also on the scene.

The Associate Press reported that oil from the slick had reached Hysham, Mont., by late Saturday night, a distance of nearly 100 miles east of Laurel.

"Nobody's been able to lay their eyes on the pipe," Peters told the AP. "Right now, the Yellowstone River is at flood stage. The bank isn't stable enough for anybody to get close."