At least 33 are reported missing after collapse at Indonesia's Freeport mine

The Grasberg gold and copper mine in the Indonesian province of West Papua.

DENPASAR - At least 33 people are missing after a training tunnel at the massive Grasberg gold and copper mine in Indonesia's West Papua province collapsed, according to mine owner Freeport-McMoRan Copper & Gold Inc. 

"A tunnel in the underground training area collapsed, trapping a number of employees," said Freeport in a statement, which was reprinted by Reuters. "The rescue process is difficult and will take some time to complete."

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The collapse, which took place early Tuesday morning, took place near the entrance to the Big Gossnan Mine, wrote Dow Jones, while Freeport maintains that early reports of fatalities were unconfirmed. 

Four were rescued from the mine and given medical treatment, according to Reuters, while three managed to get away from the collapse with no injuries. According to Dow Jones, one employee suffered broken bones. 

"Freeport Indonesia does not expect this event to have a material effect on mining and milling operations or development activities," added Freeport in its statement, noted Reuters. 

Strikes at the hugely lucrative mine have been commonplace since it was founded in the 1970s, and 2011 saw a three-month-long strike by Freeport employees, the longest such labor dispute in Indonesian history. 

A brief three-day strike at the beginning of May ended after Freeport came to an agreement with contract laborers at the Grasberg mine. 

The Grasberg mine is the largest gold mine on the planet and the third-largest open pit copper mine, and Freeport expects 2013 sales to approximate 1.1 billion pounds of copper and 1.25 million ounces of gold, up considerably from 2012.