Vale SA, the world's second-biggest nickel producer, may build an underground mine at its Voisey's Bay unit in Canada, extending the life of the deposit by 30 years.

Voisey's Bay, which started output in 2005 in Newfoundland & Labrador, is forecast to last until 2019 as an open-pit mine, said Tom Paddon, Voisey's Bay general manager. Voisey's Bay could continue producing as much as 50,000 metric tons a year through 2049 if Vale decides to build the underground mine, Paddon said yesterday in an interview in Belo Horizonte, Brazil.

"We're still a long way from making a decision," Paddon said. "This may still be more than two years off."Output from an underground mine at Voisey's Bay would feed a $2 billion nickel refinery that Vale is building in Long Harbour, Newfoundland, Paddon said. The refinery is set to open in 2014 with annual capacity of 50,000 tons, he said.

OAO Norilsk Nickel is the world's biggest nickel producer.