At least 14 people are dead, 14 are still missing and 10 have been rescued after a tunnel collapsed last Tuesday at an underground mine training facility in Indonesia.
Officials said 38 Grasberg mine workers were undergoing safety training at the Big Gossan underground training facility when the ceiling collapsed.
Rescue efforts have been made difficult because of rock slides and the tunnel's instability initially required the use of hand tools until heavy-duty equipment was deemed safe to use in the search on Thursday.
More from GlobalPost: At least 33 are reported missing after collapse at Indonesia's Freeport mine
"I have visited the accident site and met with our injured employees and the loved ones of those lost in this tragic event," said Richard Adkerson, president and CEO of Freeport-McMoRan Copper & Gold.
"I am deeply saddened and disturbed by this event. Our focus continues to be continuing efforts to gain access to the victims still buried at the accident, carried out as quickly as can be done safely. The entire Freeport family around the world joins Freeport Indonesia in grieving for our lost brothers."
Around 1,000 workers demonstrated near the collapsed mine Wednesday in the latest protest against poor working conditions that have hindered production in recent years.
Grasberg miners staged a three-month strike in 2011 that was resolved when an agreement for a significant wage increase was reached.
Grasberg mine, owned by US mining firm Freeport-McMoRan Copper & Gold, is the second largest copper mine in the world and has the world's largest gold reserves.