Sumitomo's San Cristobal mine in Bolivia has been shut down after protestors took over a key power station that supplies the mine in the southern Potosi region.
Protesters in Potosi have been demonstrating for two weeks to demand the government carry out development projects in the mineral-rich region.
Production at Cristobal was halted as a precautionary measure.
Bolivia's Mining Minister Jose Pimental said the production shutdown could cost the company up to $2m a day in lost exports.
San Cristobal is one of the largest mines in Bolivia, producing some 1,300t of zinc-silver ore, and 300t of lead-silver ore a day.