CHARLOTTE, N.C. -- An environmental group plans to ask a federal judge to stop Duke Energy Corp. from building a new coal-fired generator already under construction in western North Carolina.

Southern Environmental Law Center spokeswoman Melinda Pierson said her group will file the complaint Wednesday in U.S. District Court in Asheville. The lawsuit claims Duke has violated the federal Clean Air Act by not using the best available technology to capture mercury and other hazardous pollutants that will be discharged from the plant.

They want construction stopped until the case is resolved. Duke is building a $2.4 billion, 800-megawatt unit at its Cliffside Steam Station outside Charlotte. Construction began in January.

The state recently asked Duke to provide more details about its plan to control mercury and other hazardous air pollutants from the generator.