JOHANNESBURG, Feb. 2 (Xinhua) -- More than 900 miners, who were trapped underground in a gold mine after a power failure in the Northern Free State in South Africa, have all been rescued, the mine's owner said Friday.

The operation to rescue the trapped miners at the Beatrix mine in the Northern Free State got a boost early Friday morning when power was restored at 2 a.m. (0000 GMT), said James Wellsted, spokesman of Sibanye-Stillwater which operates the Beatrix mine.

All the trapped miners have been brought to the surface, he added.

The accident is believed to have been caused by thunderstorms on Wednesday night. Strong thunderstorms damaged power lines, causing a massive power failure and making the miners unable to take elevators up to the surface.

"This is a very unusual occurrence. We haven't had this kind of thing before but obviously we will assess and see what we can learn from it," said Sibanye-Stillwater.

The company is reportedly using a generator to get the workers out of the mine. According to earlier reports, engineers had struggled with a software fault to get emergency generators to operate and re-start the lifts in the mine.