RALEIGH, N.C. (AP) -- North Carolina regulators have denied a request by environmental groups to revoke Duke Energy Corp.'s permit for coal-fired generators at its new power plant in the western part of the state.

The state Utilities Commission said Wednesday that a motion filed by the North Carolina Waste Awareness and Reduction Network did not make sufficient arguments against the commission's earlier approval to expand Duke's Cliffside Steam Station near Charlotte.

State regulators have deemed the project a minor source of pollution, but environmental groups say the company is violating federal clean air laws.