JOHANNESBURG — A building collapsed above a gold mine in South Africa on Friday, leaving about 87 people trapped, a union spokesman said.

At least 52 people were trapped when the office building collapsed, trapping an additional 35 miners below ground, said Manzini Zungu, spokesman for the Association of Mineworkers and Construction Union. Zungu said 80 other miners were rescued.

The incident occurred at the Makonjwaan Gold Mine in the eastern town of Barberton, Zungu said. The cause of the collapse is not yet known.

The rescued miners had no serious injuries and were taken to a local hospital for treatment, television news channel eNCA reported.

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