BISMARCK, N.D. (AP) — Environmental groups say the federal government should order two coal-fired power plants in western North Dakota to use more sophisticated pollution-control technology, but state officials say the matter already has been settled and no more debate is needed.

The federal Environmental Protection Agency is taking written comments through June 17 on an appeal of North Dakota’s regional haze plan approved last year. The EPA took testimony on the appeal during a pair of hearings in Bismarck on Wednesday.