Freeport Indonesia officials inspect a tunnel at Big Gossan in Timika at the Grasberg mine, on May 19, 2013

This file photo, received on May 19, 2013, shows officials of Freeport Indonesia inspecting the tunnel at Big Gossan in Timika at the Grasberg mine, one of the world’s biggest gold and copper mines high in the mountains of rugged Papua province. On May 14, a tunnel caved in at the mine, killing 28 of 38 workers undergoing safety training.