WWF in New Caledonia is urging the nickel company Vale to improve its risk management procedures following its fifth spill in five years this week.
Operations have been suspended at its Goro processing plant since Wednesday after 100,000 litres of effluent, containing some acid, ended up in a creek due to human error.
The WWF country manager, Hubert Geraux, says the real cause and effects of the spill are not yet clear.
Mr Geraux says Vale, and the government of the Southern Province which is tasked with monitoring the plant, should take the investigation of this incident very seriously.
He says they cannot let such an incident happen again.
"It's really important today to find real solutions to ensure that if this industrial project is still accepted by the local population and the Southern Province, it will have to be totally re-thought regarding the risk management."
Hubert Geraux says some locals were blocking the entrance of the processing plant but have since moved.
The suspension at Vale has prompted a jump in the nickel price to a two-year high.