LAUREL, Mont. (AP) -- An ExxonMobil pipeline that runs under the Yellowstone River near Billings in south-central Montana ruptured and dumped an unknown amount of oil into the waterway, prompting temporary evacuations along the river Saturday morning.
Company spokeswoman Pam Malek, who was at the scene, said the pipe leaked for about a half-hour, though it's not clear how much oil leaked.
The cause of the rupture wasn't known.
Brent Peters, the fire chief for the city of Laurel about 12 miles east of Billings, said the break in the 12-inch diameter pipe occurred late Friday about a mile south of Laurel.
He said about 140 people were evacuated starting about 12:15 a.m. Saturday due to concerns about possible explosions, and the overpowering fumes. He said they were allowed to return at about 4 a.m. after instruments showed fumes had decreased. He said more evacuations occurred farther downstream outside his district but those numbers weren't immediately clear.
ExxonMobil was sending a response team to the area and cleanup work had begun with crews deploying booms and absorbent towels about a mile east of Laurel along the bank of the river, where a thick band of oil could be seen coating vegetation.
There appeared to be no attempts at capturing oil farther out in the river, and Peters said there is likely more oil washed up downstream.
"Nobody's been able to lay their eyes on the pipe," Peters said. "Right now the Yellowstone River is at flood stage. The bank isn't stable enough for anybody to get close."
The cause of the break is not known, but Peters and Malek said speculation involves high water flowing through the river that might have gouged out the river bed and exposed the pipe, which was possibly hit by debris.
"I haven't seen it this high for at least 15 years," Peters said.
The state has received record rainfall in the last month and also has a huge snowpack in the mountains that is melting, which has resulted in widespread flooding in recent weeks.
Three oil refineries are in the Billings area, and Peters said he asked all three to turn off the flow of oil in their pipelines under the river once the leak was reported. He said ExxonMobil and Cenex Harvest Refinery did so, and that Conoco Phillips said its pipe was already shutdown.
He said the river where the leak occurred is about 250 yards wide, and that early Saturday morning an oil slick appeared to be about 20 feet wide.
"That was the farthest my flashlight would reach," he said.
Laurel, which has a population of about 6,500, is known for a huge Fourth of July fireworks display put on by the fire department, which has its own pyrotechnics crew. Peters said the town can swell to as many as 50,000 people for the event.
He said the fire department plans to hold the event on Monday.
(Copyright 2011 by The Associated Press. All Rights Reserved.)