A South African trade union says nine workers have died in an accident at a gold mine outside Johannesburg.

The trade union Solidarity says the workers were killed Thursday when their cage plummeted down a shaft at the South Deep mine, run by the Gold Fields mining company. It says a snapped cable likely caused the crash.

The union says eight of the victims were contract workers for a construction firm, while the ninth was a Gold Fields employee.

A spokesman for the company confirmed the accident, but did not offer further details.

Earlier this week, four miners were killed in two separate accidents at Gold Fields mines.

South Africa's National Union of Mineworkers has said the accidents will persist until the mining industry invests in proper safety equipment and accepts full responsibility for the training of its workers.

In 2007, nearly 250 miners died in accidents across South Africa.

Some information for this report provided by Reuters and AFP.