SIBANYE Gold has started limited production at its fire-affected shaft at the Beatrix mine, but there is no indication yet of when the blaze will be extinguished.

Sibanye listed on February 11 and incorporates the Kloof, Driefontein and Beatrix mines unbundled by Gold Fields, which sees the new company as a catalyst in the consolidation of marginal gold mines in South Africa.

The fire broke out at No 4 shaft on February 19.

Nobody was hurt.

So far, 1,029oz of gold production has been lost and 1,961oz will be lost for every month the affected area is out of commission. Management is monitoring gas levels in the sealed-off area where the fire is burning. The area is 2,700m² and has been sealed to prevent any ingress of oxygen, in order to starve the fire and eventually extinguish it.

Judging when to reopen the affected area is critical because opening it too soon could reignite the fire. Rising levels of carbon monoxide compared to carbon dioxide levels indicated the fire was being suffocated, Peter Turner, Sibanye’s vice-president of operations, said on Tuesday.

"It could take weeks or months to extinguish the fire," he said.

The carbon monoxide reading has risen to 36,000 parts per million from 16,000 parts per million in four days.

"It means there’s less and less complete combustion in that fire," Mr Turner said.

Management will wait until the monoxide readings are higher than the dioxide levels and then for noxious gas levels to drop to acceptable levels before people enter the area.

"You don’t want to put too much oxygen in there too quickly, so at an appropriate time we’ll open the ventilation up and let air in," Mr Turner said.

Teams will then assess how much damage has been done to the working area and whether all or parts of it have been sterilised, meaning they cannot be mined.

Beatrix, which employs 3,300 workers, is in a methane-rich part of the Free State. The mine captures the flammable gas underground and flares it. A 5MW plant will be commissioned late next month to generate electricity from the gas.

The shaft generates a quarter of Beatrix’s production, producing about 7,011oz of gold a month. Beatrix has output of about 28,869oz a month.