MINNEAPOLIS --Environmentalists have filed another lawsuit seeking to prevent the U.S. Forest Service from swapping land for the planned PolyMet copper-nickel mine in northeastern Minnesota.

PolyMet needs the land for its mine near Babbitt. The deal calls for trading 6,650 acres of federal land for a similar amount of private land.

But a lawsuit filed in federal court Monday by the Minnesota Center for Environmental Advocacy, the Center for Biological Diversity and the Duluth chapter of the Izaak Walton League says the Forest Service badly undervalues the land at $550 an acre.

Attorney Kathryn Hoffman says it's a bad deal for taxpayers. Another group, WaterLegacy, filed a similar lawsuit in January. The Forest Service has yet to file its response to that lawsuit, and PolyMet has asked to have it dismissed.