South Africa's AngloGold Ashanti said Sunday it had suspended operations at its Mponeng mine after at least 164 employees tested positive for coronavirus.
AngloGold Ashanti said it had tested 650 workers at the gold mining site in Merafong, Gauteng province, after a first case was detected last week.
"This process has indicated 164 positive cases with only a handful of tests left to process," the company said in a statement, adding that the "vast majority" of cases were asymptomatic.
Operations at Mponeng mine have been "temporarily halted" to complete contact tracing and "sanitize the workplace".
The world's deepest gold mine resumed operations at 50 percent late last month after it was shuttered by a nationwide anti-coronavirus lockdown on March 27.
Mining is a critical element in South Africa's already struggling economy, contributing eight percent to overall gross domestic product and raking in 45 percent of foreign exchange earnings.
Mines are also one of the largest employers, with nearly half a million workers.
Limited mining activities were allowed to resume about a month ago under "strict health conditions".
But workers and unions expressed concern about returning to work in underground tunnels that could easily become breeding grounds for the novel virus.
A labour union won a court case earlier this month forcing the government to impose strict protective measures for miners.
Employers have since rolled out extra health controls, including regular screening and testing, social distancing and cleaning.
Miners with underlying chronic illnesses such as diabetes, cancer and AIDS are not allowed back to work until the virus has abated.
Before AngloGold Ashanti's announcement, there were just 85 confirmed coronavirus cases in the whole of South Africa's mining industry, including one death.
Another mine owned by Impala Platinum was temporarily shut earlier this month after 19 of its employees tested positive.
South Africa has the highest number of coronavirus cases on the continent, with 21,343 infections detected so far and 407 fatalities.