The 12-inch Silvertip oil pipeline near Billings, Mont., ruptured July 1, spilling about 1,000 barrels of crude oil into the Yellowstone River. The Billings Gazette in 2006 reported that Exxon Mobil, the owner of the pipeline, was pumping oil from tar sands in Canada through the Silvertip pipeline.
Montana Gov. Brian Schweitzer in a letter to Exxon officials last week requested information about the type of crude spilled from the pipeline.
Floodwaters along the Yellowstone River had affected cleanup operations. The U.S. Environmental Protection Agency said operations were making progress along the river as floodwaters dropped.
The EPA said 47 miles of shoreline have been assessed. Oil coverage in the area was reported as mild, with around 10 percent of any given area covered by oil.
"We are also finding large, more heavily oiled flood debris piles at various locations along the shoreline and on the islands," the EPA said in a statement.
The EPA added that U.S. wildlife officials have reported, but haven't captured, 19 "oiled" animals, including a bald eagle. Rescue workers are analyzing 10 dead animals and five others were captured for cleaning.