Sibanye Gold Ltd. suspended all operations at the Cooke gold mine Gauteng, South Africa, after a clash between two of South Africa's rival unions left two of its employees in critical condition, Reuters reported Oct. 4, citing a company spokesman.

"No one went underground last night and no shifts began this morning," the spokesman said.

The two injured miners belonged to the National Union of Mineworkers, who were attacked by members of the Association of Mineworkers and Construction Union after an argument over union numbers, NUM spokesman Livhuwani Mammburu told Reuters.

The rivalry between the two unions has been ongoing since the AMCU ousted the NUM as the dominant union in the country's platinum industry in 2012.

The mine produced about 100,000 ounces of gold in the first half of 2016, according to the report, which accounts for about 13.5% of the company's total gold output.

Sibanye shares were down by over 3% in Johannesburg.