Four workers have been pulled alive from a tunnel which caved in Tuesday at a mine in remote eastern Indonesia but police said around 30 were still trapped underground.
The accident happened at Freeport-McMoRan's Grasberg, one of the world's biggest gold and copper mines which has been hit by a string of problems including a major 2011 strike that affected production.
"Four people have been evacuated alive with injuries, and around 30 more are still trapped underground so we don't know their condition," local police chief Jermias Rontini told AFP.
He said those evacuated were sent to hospital but he did not know their conditions.
Rontini said he was not hopeful for those still trapped. "In the past, similar tunnel collapses caused fatalities as people who were trapped couldn't get enough oxygen."
The tunnel at the mine high in the mountains of rugged Papua province caved in around 8:00 am (0100 GMT) and access had proved difficult, said Rontini.
The Indonesian subsidiary of US firm Freeport said the tunnel collapse happened in an underground training area, adding that the rescue was "difficult and will take some time to complete".
The company said it did not expect production to be affected.
It did not disclose the nationalities of those involved in the accident, although the vast majority of the more than 24,000 workers at the mine are Indonesian. Neither police nor Freeport said why the accident happened.
The 2011 strike lasted three months and crippled production, only ending once the firm agreed to a huge pay rise.
The industrial action sparked a wave of deadly clashes between police and gunmen around the mine, with at least 11 people, all Indonesians, killed.
Earlier this month some 1,100 workers employed by Freeport contractors staged a three-day strike over pay but it caused only minimal disruption to production.