Talvivaara said most waste water leaked from the gypsum pond had been contained in the mining area by a fourth safety dam. According to company spokesman Olli-Pekka Nissinen, the leak site has been isolated.
"No further release of the leakage water outside the mine area is anticipated," the company said in a statement on Wednesday.
On Tuesday officials said heavy metals in water samples near the mine had risen to a level poisonous to fish and other organisms and could cause fish deaths in the area.
The leak caused waste water to gush into the mine's surrounding environment for over a week.
