Exxon Mobil, the largest U.S. oil company, said a leak at a Montana pipeline is confined to a 10-mile area around the state's largest city, Billings, and that there is little pollution around the Yellowstone River. The incident was originally reported on Saturday.
Texas-based Exxon (XOM) is conducting flights over the region to look any oil that may drifting downstream. Local officials have said flooding has hampered the cleanup work, and that some of the leaked oil could reach the Missouri River, of which the Yellowstone is a tributary, according to the Wall Street Journal.
Exxon estimated that 750 to 1,000 barrels of crude leaked in the Yellowstone and the incident forced the evacuation of local residents. The pipeline was shutdown six minutes after the loss pressure was detected, the Journal reported. The Silvertip pipeline usually moves about 40,000 barrels per day.
The U.S. Pipeline and Hazardous Materials Safety Administration audited the pipeline's integrity management program in June, the Journal reported. Exxon said the pipeline met all regulatory requirements when it underwent a more rigorous inspection in December 2010.