A second accident at Freeport McMoRan's copper mine in Indonesia's Papua province in under three weeks, threatened on Friday to cause a prolonged closure there, and hit global supplies of the metal.
The company says a driver is fighting for his life after his truck was covered in wet muck, prompting a union official to call on his members to stop work at Grasberg, the world's second-biggest copper mine.
The latest accident also raised questions over how much longer Freeport will be able to supply its customers and further strains relations between the firm and labour unions.
Freeport Indonesia said in a statement the company regrets that an accident occurred while it was performing approved maintenance activities in the Deep Ore Zone underground mine.
Earlier on Friday, Papua-based union official Virgo Solossa asked the company to stop all activities at the remote complex, and to review safety systems.
Freeport suspended operations at the complex in eastern Indonesia on May the 15th, a day after a training area in another tunnel, away from the site of its main operations, caved in on 38 workers.
Twenty-eight people died in the disaster, one of the worst mining accidents in Indonesia's history.