BILLLINGS, Mont. (AP) — Two conservation groups are suing to block a Montana logging project next to Yellowstone National Park.

Native Ecosystems Council and the Alliance for the Wild Rockies filed their federal lawsuit Tuesday in Missoula.

The Custer Gallatin National Forest proposes logging and thinning nearly 9 square miles (23 square kilometers) north of Hebgen Lake.

The U.S. Forest Service says the project will help protect homes and infrastructure.

The conservation groups say that's a prime migration corridor for Yellowstone wildlife.

They say the Forest Service approved the project without an in-depth environmental analysis after illegally amending the Custer Gallatin forest plan to loosen standards for habitat protection.

Hebgen District ranger Jason Brey tells The Billings Gazette that the amendment's aim is to remove or correct outdated and unnecessary rules from the forest plan.

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Information from: The Billings Gazette, http://www.billingsgazette.com