Freeport-McMoRan Copper & Gold stopped operations at its Grasberg mine in Indonesia for safety reasons after striking workers blocked the way and following four deaths near the mine last week, according to The Wall Street Journal.

“All accesses are blocked,” by striking workers, said PT Freeport Indonesia spokesman Sinta Sirait, including the main entrance to the mine and the seaport that it uses. He said the company doesn’t know yet when it will resume operations. Last week, the Freeport Indonesian unit operated at 80% of its capacity by using contract workers.

Workers at the Grasberg mine began a strike a month ago, demanding a big increase in the minimum wage, now at $1.50 an hour. The company and its union still haven’t reached an agreement despite the government’s efforts to mediate.

Tensions have risen around the mine since October 10, when one striker was killed and more than 10 others were injured in a clash with police. Later in the week, three workers were shot and killed near the mine and two policemen were injured by unidentified gunmen.

The violence and the escalation of the strike could slash profits from the mine, which sits atop some of the world’s largest copper and gold deposits. Production has also been affected by damage to the pipeline used to carry gold and copper concentrates, cut in several places in what could be sabotage, the company said.

Freeport facilities have been the target of violence in the past. A 2009 sniper attack on one of the mine’s roads killed three people. Seven years earlier, two schoolteachers from the U.S. were killed in an ambush on Freeport roads.