Freeport McMoRan Copper and Gold Inc ( id="symbol_FCX.N_0"> FCX.N ) was ramping up production at its Indonesian unit on Monday, a company spokeswoman said, six weeks after a deadly tunnel collapse at the world's No.2 copper mine halted operations. Trade union workers at the Grasberg mine in remote West Papua were also returning to production work, while postponed pay talks with the Arizona-based firm have been resumed, a union official added. Freeport Indonesia employs about 24,000 workers, of which three-quarters belong to the union. Freeport stopped production at Grasberg on May 15, a day after a training area in a tunnel caved in, killing 28 people. Planned pay talks were also put on hold last month. On Saturday, the company said it had slowly resumed open-pit mining after receiving approval from the Indonesian government, although underground production remained closed. "We herewith confirm that we have started to ramp up production since Saturday,&qu