JOHANNESBURG — South African media say about 900 miners are trapped underground at a gold mine after a shaft elevator stopped working because of a power outage.

The African News Agency reports Thursday that the miners are believed to be safe while they await evacuation from the Beatrix mine in Free State province.

Mine unions are expressing concern, saying some of the trapped miners could suffer from dehydration or might lack access to medication. Colleagues of the miners say they are helping to deliver food and water to them.

A thunderstorm caused the power outage at the mine, which is run by the Sibanye-Stillwater company.