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.
The miner and commodities trader is embroiled in a legal tangle over its copper and cobalt operations in Democratic Republic of Congo, where conflict and changes to regulations have deterred many mining firms.
