Exxon Mobil reported that around 1,000 barrels of crude oil spilled July 1 into the Yellowstone River from its 12-inch Silvertip pipeline near Billings, Mont.
The U.S. Environmental Protection Agency in a statement last week said crews were "finding numerous, heavily oiled flood debris piles at various locations along the shoreline and on the islands."
The EPA said many of the debris piles would need to be hauled off and run through a wood-chipper. This could require Exxon to add to the 750 people designated for cleanup operations, Bloomberg News.
State officials last week, the news agency adds, warned residents that fish taken from the Yellowstone River near the site of the spill could contain toxins from the spill. Air quality alerts were issued shortly after the July 1 accident.