World's Biggest Copper Mine Closed Because of Strike
Escondida mine in Chile
Some 2,500 workers at the world's biggest copper mine, in northern Chile, have begun an unannounced strike over pay and other demands.
The strike at the Escondida mine was initially planned to last 24 hours, union leader Marcelo Tapia said.
But the movement's officials will meet again to assess whether to extend it.
Chile produces a third of the world's copper, a metal widely used in alloys and electric cables.