The leak, which allowed water containing nickel and uranium to seep into the environment of the Kainuu mine, was thought to be sealed up after efforts that went on throughout Thursday night.
It is estimated that over 10,000 kilos of nickel as well as unknown amounts of uranium may have leaked into the mine's surroundings.
Talvivaara CEO Harri Natunen said he had received information that the leak had indeed been plugged.
”Now we will minimise leakages from overflow pools [surrounding the gypsum pond]. Any leaks will also be neutralised so that metals cannot contaminate nature,” Natunen said.
The Talvivaara CEO admitted that the back-up pools were rather full, but he maintained these should hold up.
”We are now quickly constructing a safety dam that will contain everything. We are in a race with time,” Natunen added.
The Kainuu Employment and Economic Development Centre said on Thursday evening that the gypsum pond should not have been used for storing waste water, and that no special permit had been granted for this.
“We had a really rainy summer. We observe our drainage permit, which allows us to drain 1.3 million cubic meters of water into the environment annually. However, we reached this limit already in November, which is why we had to keep all the waste water in our pools,” Natunen explained.
Busy days for Ville Niinistö
Environment minister Ville Niinistö visited the crisis-hit mine on Thursday, calling the latest leak a 'serious environmental crime'.
Later in the day the opposition grilled the cabinet over what it saw as dodging responsibility in the environmental disaster. Niinistö promised that the mining company would be brought to justice over breaches of environmental permits, and encouraged people in the Talvivaara area to seek damages for the pollution.
Natunen says everyone has a right to do so, and that Talvivaara would pay the compensations it was responsible for. The mining CEO was unable to estimate the total sum run up by such compensations.
Speaking on Yle TV on Friday morning, Niinistö also blamed ministers of the previous government, and the legislation and administrative reforms carried out during their term.
Niinistö is setting up a working group to probe the leak as well as officials' involvement in the matter.