From this story in USA Today:
_Residents along portions of the oil-contaminated Yellowstone River are expressing frustration over the lack of information flowing from ExxonMobil, state and federal officials following last weekend's pipeline burst. An ExxonMobil pipeline that runs under the Yellowstone River near Laurel, Mont. ruptured near midnight Friday and leaked hundreds of barrels of oil into the river, contaminating riverbanks and flooding fields for miles. Montana Democratic Gov. Brian Schweitzer estimates that the contamination may have spread more than 270 miles downstream into North Dakota.
_North Dakota Water Quality Director Dennis Fewless said that he's been in contact with Montana officials and the Environmental Protection Agency. He says officials are taking water samples in the Williston area as a precaution. Company and federal officials said they have only seen oil about 25 miles downstream from the site of the break near Laurel.