About 87 people are trapped after a building collapsed at a gold mine in South Africa, a union has said.

The Association of Mineworkers and Construction Union said 52 people were trapped when an office building collapsed above ground in the town of Barberton in eastern Mpumalanga province, trapping an additional 35 miners below ground.

Spokesman Manzini Zungu said 80 miners had been rescued. Television news channel eNCA said the rescued miners had no serious injuries.

The cause of the collapse at the Makonjwaan Gold Mine is not yet known.

It is the second accident in a South African mine in the past two weeks, Mr Zungu said.