At least 13 workers have been wounded by machetes and rubber bullets in the latest wave of violence to hit a South African mine.
Police said the attacks at the Anglo American Platinum (Amplats) site in Rustenburg were provoked by a dispute between two rival unions.
The news agency Reuters said around 1,000 members of the Association for Mineworkers and Construction Union gathered at the mine, about 70 miles northwest of Johannesburg, after four people believed to belong to the National Union of Mineworkers tried to occupy an office.
Security guards at the mine used rubber bullets to disperse the rival groups.
A police spokesman said the 13 injured workers were admitted to hospital.
Anglo American (LSE: AAL.L - news) , which owns the mine and is listed on the London Stock Exchange (LSE: LSE.L - news) , saw a 2.75% fall in its share price on the FTSE 100 (FTSE: ^FTSE - news) when news of the trouble emerged.
The violence follows a two-month illegal strike at the same site last autumn, when police fired rubber bullets, tear gas and stun grenades to separate groups of workers.
The continuing dispute is related to anger over Amplats' plans to lay off an additional 14,000 workers amid poor company results which showed a loss of $225m (£143m) for 2012.
It is among several mining companies in South Africa grappling with higher expenses amid the worst industrial action the country has seen for decades.