State officials are issuing an order to Duke Energy that it says is aimed at stopping “the continued spread of coal ash contamination in the groundwater” near a Wilmington power plant.

The N.C. Department of Environment and Natural Resources issued the notice of regulatory requirement to the nation’s largest utility on Tuesday after recent tests in the vicinity of the L.V. Sutton Electric Plant in New Hanover County showed high levels of boron, a metal that is a recognized indicator of coal ash contamination.

The metal was found in monitoring wells at or beyond the facility’s compliance boundary as well as three water supply wells approximately half a mile from the plant.

The levels of boron in the water supply wells did not exceed state groundwater standards but were much higher than concentrations found in background wells in the area, state officials said in a statement.

“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,” said Tom Reeder, an assistant secretary for DENR. “We are ordering Duke Energy to immediately take corrective actions to prevent further migration of coal ash contaminants.”

The utility has until July 9 to control and prevent further migration of coal ash contaminants and submit a plan to monitor for the effectiveness of its actions. Failure to meet the state’s requirements may result in a fine.

The state fined Duke Energy $25.1 million on March 10 for violations of groundwater standards at the plant, the largest-ever penalty for environmental damages.

Separately, the state’s environmental agency said it has hired Kilpatrick Townsend & Stockton for legal services related to Duke Energy’s decision to contest the $25.1 million fine DENR issued to the utility in March for groundwater contamination at its Sutton Plant near Wilmington. The law firm, together with the state Attorney General’s office, will represent DENR through all phases of the litigation.

DENR issued a strongly worded statement expressing concern that Duke Energy was contesting the fine.

“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,” said DENR’s General Counsel Sam Hayes. “In addition to the Attorney General’s office, the state has hired outside counsel to form the best legal team possible to make sure Duke Energy is held accountable for its assault on the environment.”