CAPE TOWN, Dec. 7 (Xinhua) -- Four miners remained trapped underground at a South African gold mine following a tremor, authorities said on Saturday.
Five miners were working underground when the tremor occurred on Friday, causing a rockfall at the Tau Lekoa Gold Mine in Orkney, northeast South Africa, the National Union of Mineworkers (NUM) said.
A miner was rescued with serious injuries while four others were trapped underground, according to NUM.
A rescue team lost contact with the four miners early Saturday after one of the miners said they were suffocating and desperately need oxygen, NUM president Joseph Montisetse said.
The miners "might not be in good health," said Montisetse.
As rocks continued to fall underground, it would take three to four days to rescue the miners, NUM said in a statement.
The union called for "drastic action" to improve the safety standards and procedures at mines.
Labor unions have complained about mining companies forcing miners to work in unsafe areas, thus pushing fatalities to "crisis levels."
South Africa recorded 88 deaths in the mining sector in 2017 and 81 deaths last year.
