More than 100 people are reported to be trapped after a mine collapsed in Mpumalanga Province in northeastern South Africa while 49 of the miners have been rescued, emergency services said.
South Africa's mines are the deepest and among the most dangerous in the world.
Manzini Zungu, spokesman for the Association of Mineworkers and Construction Union (AMCU), said that around 115 people have been trapped inside the Makonjwaan Gold Mine in Barberton, Mpumalanga province, at 8:40 a.m. (0640 GMT).
However, the cause of the accident is still not known.
"At this point it's unclear what caused the disaster," Zungu said
The mine is located about 360 km east of Johannesburg.
Deaths due to mine accidents have surprisingly decreased as safety practices improve by time and lab or force is less and less as production has also been reduced.
Last year, 77 workers were killed in mining accidents, the lowest number on record.