There are fears of massive job losses in New Caledonia as a result of continued vandalism at the Kouaoua mining site.
Another fire has damaged the belt system which feeds nickel ore to the coast for shipping to the SLN nickel smelter in Noumea.
It is the third such incident in a year, causing substantial material damage each time and interrupting operations for days while repairs are made.
The mayor of Kouaoua said he was exasperated by the attacks and feared that SLN might shut down the site, on which about 400 jobs depend.
In the past, he implored locals to break the code of silence and help catch those who keep setting fire to the 11 kilometre conveyor belt system.
Reports said it was unclear who was behind the attacks and who was being targeted.
An SLN spokesperson said questions needed to be asked about why a work place was being damaged.
SLN, which is New Caledonia's biggest private sector employer, has been running at a loss because of a drop in the price of nickel.