Last week’s resumption of work by Freeport McMoRan Copper and 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 collapsed on 38 workers, killing 28 and leaving 10 injured. Underground work was still suspended during the latest incident this weekend when wet ore material leakage from a bin covered a truck and during “approved maintenance,” according to company officials; the operator died at a local hospital.  

Normally, the massive Grasberg mine produces some 220,000 tons of concentrate daily, with 140,000 tons from open-pit mining and 80,000 from underground; a 90-day stoppage at Grasberg, say observers, would remove some 125,000 copper tons from of 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 Dorector Dede Suhendra told Reuters on Monday.

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