New Caledonia's appeal court has fined the Vale nickel company 5,000 US dollars over an acid spill at its Goro plant three years ago.
Noumea's daily newspaper reports that the fine is the highest possible under the southern province's environment code.
The ruling was prompted by a complaint by an environmentalist organisation, which says its persistence alone led to results after a police probe had been without consequence.
The spill of more than 40,000 litres of acid was not contained and about 2,000 litres ended up in a lagoon which is a World Heritage site, killing nearly 2,000 fish.
Two years ago, the Vale plant spilled 670,000 litres of a solution containing acid but the company said nobody was injured and the spill was contained by the tailing dams.
The plant, which cost about four billion US dollars to build, is yet to come into full production.