JOHANNESBURG - Police said on Monday they were investigating the death of six people who were trapped underground at Phalaborwa copper mine in Limpopo province in the early hours of Sunday.
The National Union of Mineworkers (NUM) said the incident added to an unacceptably high number of mine fatalities this year.
Police said a joint operation led by search and rescue teams was activated soon after the incident was reported, with the first body retrieved during the day on Sunday. Five more bodies were found in the early hours of Monday.
"The deceased are all men and the process of identifying them is still unfolding," a police statement said.
"The cause of this incident is still not clear at this stage but the police investigations in conjunction with other role players including the affected mine will tell as they are still continuing."
NUM said it had been informed the men were killed after fire erupted due to high temperature underground.
"We vehemently condemn this kind of incident as there is a high number of fatalities in the mining industry in South Africa this year," it said.
"We further urge the department of mineral resources which is the regulator to play its role in ensuring that mines are safe and put the safety of the mineworkers as a priority."