BOISE, Idaho (AP) — A federally-run sheep research facility operating in eastern Idaho and long targeted by environmental groups concerned about potential harm to wildlife is facing another legal challenge.

The U.S. Department of Justice in court documents filed Monday in response to a lawsuit says the U.S. Department of Agriculture's Sheep Experiment Station correctly followed environmental laws in authorizing sheep grazing.

Western Watersheds Project and two other groups in a lawsuit filed in February are challenging a decision allowing sheep owned by the University of Idaho to graze in the Centennial Mountains of Idaho and Montana this year.

The groups say the areas contain essential wildlife habitat that's a corridor for grizzly bears between Yellowstone National Park and central Idaho.

The groups also say bighorn sheep and greater sage grouse use the area.

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