The French metals firm Eramet says the blockades of its operations in New Caledonia shows that the level of labour unrest in the territory is becoming more serious.
The company's president director-general, Jacques Bacardats, says labour disputes have cost Eramet 2-thousand 5-hundred tonnes in nickel production since the beginning of the year.
The union CST is blocking three mines in New Caledonia run by Eramet's subsidiary, SLN.
CST is protesting against the dismissal of four employees, but Eramet is now threatening to sack everyone at the blocked mines.
Mr Bacardats says the workers can't continue in an environment in which people can no longer work.
A conflict between shareholders in one of SLN's subcontractors, Soren, has led to the interruption of the supply of nickel ore to the territory's only smelter.
The smelter needs a constant supply of ore to be able to operate.
Stocks to hand are now running low and the action threatens a catastrophic shutdown.
Mr Bacardats says it may lead to what he calls a 'very dangerous situation'.