The Grasberg mine in Indonesia's Papua province has been ordered to suspend production by the government after reopening its operations last week.
Owner Freeport McMoRan's President in Indonesia Rozik Soetjipto was defiant last week, saying it was a matter for the company to decide.
The All Indonesian Workers Union says workers will not return until Freeport suspends officials believed to be responsible for a tunnel collapse last month, in which 28 workers were killed.
A truck driver was killed on Friday in a separate incident.
An employee and member of the union Darmawan Puteranto says he supports the Government's strong stance and says more should be done to hold the company to account.
"It's very very extreme, because 28 persons dying, it's not a small number, it's a big number and with the Indonesian Government, the sanctions should be very hard."
Mine worker Darmawan Puteranto.