Last week’s resumption of work by Freeport McMoRan Copper & Gold Inc. at its Indonesian copper mine, following one of the country’s worst mining disasters, was halted by government officials amid an investigation that could last three months after a second unrelated fatality.

Phoenix-based Freeport initially halted open-pit operations at the world’s second-biggest copper mine on May 15 after a tunnel collapse killed 28 and left 10 injured. The latest incident occurred after wet ore material flowed from an ore bin covering a truck and its operator during underground “approved maintenance,” according to company officials. The man later died at a local hospital.

Normally, the massive Grasberg mine produces some 220,000 metric tons (mt) of concentrate daily, with 140,000 mt from open-pit mining and 80,000 mt from underground. A 90-day stoppage at Grasberg, observers said, would remove some 125,000 mt of copper from the global supply chain.

Freeport open-pit and underground operations may now be closed up to 90 days, pending the investigation’s outcome. “While the investigation is ongoing, there cannot be any production, except maintenance,” Minerals Resources Director Dede Suhendra told Reuters on Monday.

Freeport officials plan to transform Grasberg into the world’s largest underground copper mining project after 2016 when open-pit operations are slated to end; open-pit mining currently accounts for two-thirds of production. Analysts noted that a protracted closure of the Grasberg complex will likely have serious impact on copper and gold prices.