The government has been notified by Lesotho of the deaths of at least 31 suspected illegal miners in a ventilation shaft at Virginia mine in Welkom, Free State.
The accident occurred on May 18, the department of mineral resources and energy said .
Three bodies are reported to have been retrieved and brought to the surface by other illegal miners.
The shaft was last operational in the 1990s.
Efforts to retrieve the bodies of the men, believed to be Basotho nationals, are being hampered by conditions at the mine, the department said.
"Although information on this tragic situation comes sporadically, we are doing our best to act on the information.
"Working in collaboration with the previous owners of the mine, Harmony, the department's inspectors have assessed the situation and determined methane levels in the mine ventilation shaft 5 are very high. It is too risky to dispatch a search team to the shaft.
"All relevant stakeholders will endeavour to ensure the suspected deceased illegal miners are brought to the surface."
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