Rescuers are working for a fourth day to dig through a caved-in tunnel at a giant U.S.-owned gold and copper mine in Indonesia to try to reach 23 trapped workers.

The operator of the Grasberg mine in Indonesia's province of Papua, PT Freeport Indonesia, said Friday that rescuers had successfully cleared two passages to provide access for heavy equipment to help expedite the rescue efforts.

The collapse happened Tuesday when 38 workers were undergoing safety training inside a classroom in the tunnel. Ten miners have been rescued and five bodies recovered since then.

Rescuers have had to remove debris manually since heavy equipment could not be used in the tight space.

More than 20,000 workers are employed at the mine owned by Phoenix, Arizona-based Freeport-McMoRan Copper & Gold Inc.