A worker has been critically injured in an accident at a giant U.S.-owned mine in Indonesia two weeks after the collapse of an underground room killed 28 people.

Mine operator PT Freeport Indonesia says liquid ore material flowed into a truck during maintenance activities on Friday, injuring its driver.

It says the driver has been hospitalized in critical condition.

On May 14, the roof of a tunnel inside the Big Gossan facility collapsed, killing 28 of 38 workers who were undergoing safety training in an underground classroom. The company said it was reviewing safety after that accident.

The mine in the resource-rich but impoverished area of Papua province employs more than 20,000 workers. It is owned by Phoenix, Arizona-based Freeport-McMoRan Copper & Gold Inc.