Indonesia’s mining ministry expects an investigation into a deadly accident at Freeport-McMoRan Inc’s copper mine to take a week, and open-pit mining will not resume until its conclusion, a government official said on Monday.

Freeport on Saturday halted open-pit mining at its Grasberg copper mine, one of the world’s biggest, after a truck collision killed four.

“We can’t resume their operations until we know the cause of the accident. We hope it won’t take more than one week,” Sukhyar, director general of coal and minerals at the mines ministry, told reporters.

A Freeport spokeswoman said the U.S.-based company was cooperating with the government to determine the cause of the accident.

Under normal conditions, the open pit produces around 140,000 tonnes of copper ore per day and the underground puts out about 80,000 tonnes. (Reporting by Wilda Asmarini and Michael Taylor; Writing by Randy Fabi; Editing by Louise Heavens)