The smelter, which produces some 430,000 metric tonnes of aluminum annually, has been operating at reduced capacity by non-union workers since Jan. 11.
La Oroya polymetallic smelter had been operated by Doe Run Peru, a unit of the U.S.-based Renco Group, from 1997 until the company went bankrupt in 2009 and its assets were transferred to a group of former creditors.