Freeport-McMoRan Copper & Gold Inc. suspended operations at the world’s second-largest copper mine, where four people were killed and 25 remain trapped after a tunnel collapse at the Grasberg complex in Indonesia.

Mining was halted in sympathy for the victims of the accident, which had no direct impact on operations, Freeport Indonesia President Director Rozik Soetjipto said in Jakarta on Wednesday. The company has enough stockpiled material to supply shipments for as many as two days, he said.

Grasberg in Papua includes underground and open-pit operations and is the world’s second biggest by output, Freeport said in a presentation on Tuesday. The complex generated $3.92 billion of revenue for Freeport last year, or 16 percent of the Phoenix-based company’s sales. Freeport owns 91 percent of the mine, which also produces gold, and Indonesia’s government holds the rest, according to the company’s website.

Thirty-nine workers may have been in a classroom at an underground training facility when a tunnel collapsed on Tuesday, Freeport said in an e-mail on Wednesday. Ten survivors have been evacuated and are reported to be in a stable condition.

Freeport is inspecting the structure of the underground mines at Grasberg, Soetjipto said. He declined to comment on the suspension’s potential impact on production.

Before the latest stoppage, output at Grasberg was disrupted in both 2011 and 2012 after labor unrest and violence. The company said in a February filing that 15 people died and 57 were injured in 37 shooting incidents in and around the complex between July 2009 and February 15.

Freeport declined 1.2 percent to $31.21 at 9:30 a.m. in New York.

Bloomberg