The chief of Exxon Mobil Corp. pledged on Monday to do whatever necessary to mop up the pipeline oil leak into the Yellowstone River as the company intensified its cleanup of spilled crude, according to media reports.

Under political pressure, Exxon Mobil Corp. acknowledged that its pipeline leak could extend far beyond a 10-mile (16-kilometer) stretch of the famed waterway.

"We're not limiting the scope of our cleanup to the immediate site," Exxon Mobil Pipeline Co. President Gary Pruessing said at a news conference along the river near Laurel, as crews mopped up oil in the background.

Exxon Mobil has estimated that up to 1,000 barrels, or 42,000 gallons (159,000 liters), of crude oil spilled Friday night before the flow from the damaged pipeline was stopped.

Pruessing said air and water monitoring had not revealed any health risks and the officials from the Environmental Protection Agency were still taking air and water samples to determine the impacts.

Though the cause of Montana spill has not yet been determined, officials speculated that high waters in recent weeks may have scoured the river bottom and exposed the pipeline to debris that could have damaged the pipe.

The 20-year-old Silvertip pipeline delivered 40,000 barrels a day to a refinery in Billings along a route that passes beneath the river.

The U.S. Department of Transportation, which oversees pipelines, notified Exxon Mobil in July 2010 of seven potential safety violations and other problems along the pipeline.

The Yellowstone spill has underlined calls from some safety advocates and environmentalists who want the government to impose more stringent regulations on the industry.