Four miners were killed and three others were trapped underground after an earthquake hit a gold mine outside Johannesburg, its owners said Friday.
Thirteen miners were initially trapped about three kilometres (two miles) below the surface, James Wellsted, spokesman for mining company Sibanye-Stillwater, said in a statement.
Six of the rescued workers have been hospitalised.
Wellsted said the epicentre of the 2.2-magnitude quake was close to where the miners were working on Thursday.
Operations at the Masakhane mine in Driefontein have now been suspended.
The National Union of Mineworkers (NUM) said it was “angry and concerned at the rate at which mining incidents are happening at Sibanye-Stillwater.”
In February, nearly 1,000 miners were trapped underground for 30 hours following a power cut caused by a storm in another mine owned by Sibanye-Stillwater.
A few days later, two miners were killed after ground collapsed at a mine also belonging to the group.
The South African Federation of Trade Unions (SAFTU) has called for the government to investigate the accident and take action to prevent any further tragedies.
“This latest tragedy was caused by a seismic shift, but these are a hazard that can be expected in deep mines and research must be done to find ways of managing their impact on those working underground so that no more lives are lost,” SAFTU said.
Mine accidents are common in South Africa. In 2016, 73 people died in mines around the country, according to figures from the Chamber of Mines.