A pipeline operated by Exxon Mobil Corp leaked as many as 1,000 barrels of crude oil into the Yellowstone River in Montana and has been shut down, Reuters reports citing the company's statement.
Exxon officials said on Sunday there were traces of oil up to 10 miles downriver from the site of what they called a "very unusual" event, though the governor of Montana said the spill may have spread further.
The U.S. oil company said it had slowed processing rates at its Billings refinery following the leak but did not expect supply disruptions in the area.
Exxon found the leak from the EMPCo pipeline early on Saturday morning. The pipeline runs only in Montana, from Silver Tip to Billings.
The cause of the leak remains unclear. Exxon estimated the oil release at anywhere from 750 to 1,000 barrels. One barrel of oil is equivalent to 42 gallons (163 liters), and the pipeline typically transports 40,000 barrels a day.
"We had no indications that there were any issues with this pipeline," Gary Pruessing, the president of EMPCo, told reporters on a conference call on Sunday.
Pruessing said the pipeline had been shut in May as a precaution as the river approached a high-water point, but that it was judged to be safe and turned back on.
Montana Governor Brian Schweitzer questioned Exxon's contention that the spill into the Yellowstone, the longest undammed river in the United States, was concentrated within a 10-mile area.
A full assessment of the oil's spread will not be possible until small boats can be deployed in the river, he said.
Exxon said earlier that the river's turbulence made it unsafe to use boats, but that the company had sent aircraft to view the spill.
Exxon discovered the leak when a loss of pressure was detected on the pipeline, which dates from 1991, and within six minutes the line was shut off, company officials said.
Some residents were briefly evacuated as a precaution but were allowed to return home later.
The leak came one day after a Maryland jury awarded plaintiffs suing Exxon $1.5 billion in damages for a 2006 leak at a gasoline station.
Exxon officials said on Sunday there were traces of oil up to 10 miles downriver from the site of what they called a "very unusual" event, though the governor of Montana said the spill may have spread further.
The U.S. oil company said it had slowed processing rates at its Billings refinery following the leak but did not expect supply disruptions in the area.
Exxon found the leak from the EMPCo pipeline early on Saturday morning. The pipeline runs only in Montana, from Silver Tip to Billings.
The cause of the leak remains unclear. Exxon estimated the oil release at anywhere from 750 to 1,000 barrels. One barrel of oil is equivalent to 42 gallons (163 liters), and the pipeline typically transports 40,000 barrels a day.
"We had no indications that there were any issues with this pipeline," Gary Pruessing, the president of EMPCo, told reporters on a conference call on Sunday.
Pruessing said the pipeline had been shut in May as a precaution as the river approached a high-water point, but that it was judged to be safe and turned back on.
Montana Governor Brian Schweitzer questioned Exxon's contention that the spill into the Yellowstone, the longest undammed river in the United States, was concentrated within a 10-mile area.
A full assessment of the oil's spread will not be possible until small boats can be deployed in the river, he said.
Exxon said earlier that the river's turbulence made it unsafe to use boats, but that the company had sent aircraft to view the spill.
Exxon discovered the leak when a loss of pressure was detected on the pipeline, which dates from 1991, and within six minutes the line was shut off, company officials said.
Some residents were briefly evacuated as a precaution but were allowed to return home later.
The leak came one day after a Maryland jury awarded plaintiffs suing Exxon $1.5 billion in damages for a 2006 leak at a gasoline station.