Gold Fields is South Africa's second-biggest gold miner
South African mining group Gold Fields faces a $7bn (£4.4bn) legal challenge from former workers, who claim they were contaminated by uranium and have now fallen ill.
Apartheid Claims Task Force (ACT) lawyer John Ngecebetsha, acting on behalf of more than 500 former workers, said he would file the lawsuit in a New York court on Monday.
"It's a case against Gold Fields for exposing former
employees to dangerous working conditions leading to uranium contamination," said Mr Ngecebetsha.
South Africa's second largest gold miner said it would "strenuously defend" itself against the suit, and that did not recognise US jurisdiction over the issue.
Uranium is often mined as a by-product of gold in South Africa.
'Nothing to hide'
Mr Ngecebetsha said the suit was not seeking apartheid reparations but damages related to working conditions, like those won for South African miners suffering from asbestos-related illnesses.
Billy Jacobsz, Gold Fields Vice-President, confirmed the company had received a letter from lawyers indicating their intention to sue.
"We are quite unsure as to exactly when it's going to happen, where it's going to happen and what the content (of the lawsuit) is going to be," Mr Jacobzs told the BBC's World Business Report.
He said Gold Fields would do whatever was necessary to defend its reputation as it has "nothing to hide".
He said levels of uranium within South Africa's gold-bearing rocks were "extremely low", and that Gold Fields operates "well within" South Africa's standards, which were "some of the most stringent in the world".
Mr Ngecebetsha and US lawyer Ed Fagan have already filed a suit against South Africa's biggest company, Anglo American and its diamond subsidiary De Beers, for $6.1bn in damages on behalf of apartheid victims.
In the 1990s, Mr Fagan headed a successful claim against Swiss banks on behalf of Holocaust victims
Gold Fields' shares are listed on the New York Stock Exchange.