— State regulators on Tuesday ordered Duke Energy to immediately halt spreading groundwater contamination from coal ash ponds at its L.V. Sutton Steam Plant near Wilmington.

Tests have found elevated levels of boron, a metal that is a recognized indicator of coal ash contamination, in monitoring wells near the plant and in three water supply wells about a half-mile away, according to Department of Environment and Natural Resources officials.

"The levels of boron in these wells are a clear indication that coal ash constituents from Duke Energy’s coal ash impoundments have infiltrated the groundwater supply," Tom Reeder, an assistant secretary for DENR, said in a statement. "We are ordering Duke Energy to immediately take corrective actions to prevent further migration of coal ash contaminants."

Coal ash is the material that's left over when coal is burned for fuel. While much of it is inert, it does contain toxic levels of certain substances, such as thallium, mercury, lead and other materials harmful to humans and wildlife.

Duke has until July 9 to stop the spread of the contamination and to submit a plan to monitor for the effectiveness of its actions. Failure to meet the state’s requirements may result in a fine, officials said.

"It is way past time that DENR and Duke Energy take action to halt the spread of groundwater contamination in Wilmington," said Frank Holleman, senior attorney for the Southern Environmental Law Center, which has sued over contamination from ash ponds at Duke plants across the state. "We gave DENR and Duke Energy notice of this serious problem two years ago and have been urging them to stop the groundwater contamination ever since. It is too bad that it took two years for something to happen, and the Wilmington community needs this protection of its groundwater supplies as soon as possible."

In March, DENR levied a $25.1 million fine against Duke for groundwater contamination near the Sutton plant. The fine, which Duke has appealed, is the largest ever imposed by DENR.

"It is evident that Duke Energy is choosing to spend its virtually limitless legal resources to fight fines for clearly documented groundwater contamination stemming from its coal ash impoundments near the Sutton plant,” DENR General Counsel Sam Hayes said in a statement.

DENR has hired attorneys from Kilpatrick Townsend & Stockton to help the Attorney General's Office represent the state in the dispute, officials said.

Duke pleaded guilty last month to violating the Clean Water Act in connection with leaks from ash ponds at other power plants and a major coal ash spill in the Dan River in 2014. The utility agreed to pay $102 million in fines and restitution and was placed on probation for five years.