DURHAM, N.C. — North Carolina officials say they have hit Duke Energy, the nation’s largest electric utility, with the largest environmental fine in state history.

The $25.1 million penalty, announced Tuesday by the State Department of Environment and Natural Resources, addresses the contamination of groundwater by coal ash from a single facility — the company’s Sutton Plant near Wilmington, N.C.

Federal prosecutors are pursuing a separate, much larger action against the company stemming from its spill of millions of gallons of toxic coal ash from a plant on the Dan River, near the Virginia border. The company said in an earnings statement that it expected to pay about $100 million in that action, which was expanded to concern Duke Energy plants across the state.

In that episode, prosecutors have filed criminal charges accusing the company of violating the federal Clean Water Act because of the illegal dumping. They also accused the company of failing to maintain equipment around at least two plants.