Cleanup and damage assessment continue Sunday after a pipeline operated by ExxonMobil ruptured Friday night near Billings, Mont., sending an estimated 750 to 1,000 barrels of oil into the Yellowstone River.

The rupture created a plume of oil that stretched some 25 miles, and oil was reportedly sighted as far west as Hysham, 100 miles downstream. Some residents in the nearby town of Laurel were temporarily evacuated, but have since been allowed to return to their homes.

The cause of the leak has not yet been determined. The company said that the pipeline was last inspected in December. Gary Pruessing, the president of ExxonMobil Pipeline, was quoted in a release saying, “We will stay with