Movement has been detected in an unused Free State mine shaft where 31 illegal miners are suspected to have died during a methane explosion last month.

Mineral Resources Minister Gwede Mantashe says the movement underground could be a sign of survivors.

The mining shaft was last used by Harmony Gold Mining more than three decades ago.

The company’s spokesperson Sihle Maake says the recovery efforts of the miners could not proceed as there are still high levels of methane gas.

The Kingdom of Lesotho informed South Africa about the suspected deaths.

It’s understood the miners who are believed to Basotho nationals died on May 18th. Three bodies were reportedly brought to surface by other illegal miners.