MARQUETTE, Mich. (AP) — Work has started at an underground nickel and copper mine in the Upper Peninsula following a 12-year legal and political struggle over the $800 million project.

Toronto-based Lundin Mining Corp. announced mining began Tuesday and it is ramping up production of nickel and copper concentrates. The mine employs more than 300 people for production and is the only U.S. mine where nickel is the primary targeted mineral.