Chile Worker's Strike at World's Top Copper Mine Chilean workers went on strike Wednesday at Escondida, the world's biggest copper mine, over demands for an annual bonus and better working conditions. Union leader Marcelo Tapia told The Associated Press that the mine's 4,800 workers walked off the job for 24 hours, but they threatened to extend the strike if their demands were not met. "We're not ruling out other scenarios that we'll be analyzing," Tapia said. This could turn into an indefinite stoppage. Chile is the world's top copper producing country and the metal accounts for about a third of government revenue. Escondida, which is in the Atacama desert, produced 1.1 million metric tons of copper last year. The mine is majority owned by Australian mining company BHP Billiton Ltd. Workers at BHP's Cerro Colorado and Spence mines joined the strike. Tapia said miners were required to work shifts that go beyond 12 hours and had complained about poor labor conditions to government officials. He said company surveillance cameras violate workers' privacy. Officials at BHP Billiton could not be reached for comment. Escondida's union staged a two-week work stoppage in 2011 that severely hit production.