Miners dig gold at Sibanye Gold Mines Ya Rona shaft, level 33 in Carletonville. 679 25.10.2015 Picture: Itumeleng English

Johannesburg - More than 100 people are trapped underground at a gold mine in Barberton, Mpumalanga, after an unspecified geological incident this morning.

In a statement issued Friday by the Association of Mineworkers and Construction Union (AMCU), the labour body says about 115 staff are trapped after the main offices at Makonjwaan Gold Mine caved in at around 8.40am.

Currently, it is not clear what caused the disaster.

Spokesman Manzini Zungu says AMCU leadership are en route to the mine. He has heard unconfirmed reports that 3 people may have died.

Zungu says it is possible that the incident was caused by a sinkhole, although Barberton is not known for such geological issues.

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Currently, says Zungu, it is not clear how far underground the miners are. He adds emergency services should already be on site to rescue those who are trapped.

Makonjwaan was one of the first open pit gold mines to be established in South Africa. It’s current ownership was not immediately clear.

Update: Reuters has since publication reported that  some 49 miners have so far been rescued after a mine shaft collapsed in eastern South Africa, trapping about 100 workers, emergency services group ER24 said.

"Mine rescue services are still busy on scene to rescue the remaining miners underground," it said in a statement.