State environmental regulators are investigating a sheen on the Monongahela River in Fairmont.
The Department of Environmental Protection tells media outlets that the substance appeared to be petroleum based.
The DEP says the substance won't affect Fairmont's water supply. The city's water intake is upstream on the Tygart Valley River.
Morgantown's water intake is about 15 to 20 miles downstream. The DEP says the Morgantown Utility Board's water intake is too deep to be affected, since petroleum based substances float on the water's surface.
The sheen was sighted Saturday. The DEP says no industry or business has reported a spill.