A US energy company has agreed to pay almost $5.5 million (£3.6m) in fines and contributions to environmental projects as part of a lawsuit.

The Environmental Protection Agency (EPA) and the Department of Justice (DOJ) announced the settlement with Duke Energy over pollution at five coal-fired power plants in North Carolina.

The EPA said it resolves claims the energy firm violated the Clean Air Act by “unlawfully modifying” 13 coal facilities without obtaining air permits and installing and operating pollution control technologies.

Duke recently shut down 11 of the 13 units, it added.

The company must continuously operate pollution controls and meet interim emission limits at the remaining two units before permanently retiring them.

EPA estimates the settlement will cut emissions by around 2,300 tons per year.

Cynthia Giles, Assistant Administrator for EPA’s Office of Enforcement and Compliance Assurance said: “This settlement brings five more power plants into compliance under EPA’s national initiative to cut pollution from the country’s largest sources. After many years, we’ve secured a strong resolution, one that will help reduce asthma attacks and other serious illnesses for the people of North Carolina.”