South African authorities now presume five miners are dead after a mudslide trapped them more than 800 metres underground at the Ekapa mine in the Northern Cape, Reuters reports. The incident occurred in the early hours of Tuesday, when a sudden “mud-rush” struck the mine.

Following an assessment of the ongoing rescue efforts, Mining Minister Gwede Mantashe said the priority has shifted to recovering the miners’ bodies. “The time passed since the event is a major concern, but there is no change in approach to the rescue activities,” Ekapa Minerals General Manager Howard Marsden said in a statement, Reuters notes.

Ekapa Minerals, which operates the mine, immediately halted all operations after the incident and has maintained contact with the families of the trapped miners, who held a vigil near the site on Thursday night. The company confirmed that rescue efforts are continuing while a formal investigation is planned to determine the cause of the mudslide.

The Ekapa mine is located near Kimberley, a historic diamond-producing area famous for a 19th-century rush that attracted prospectors worldwide. Diamond revenues from the region helped fuel the growth of South African industry and gold mining, which in turn financed Britain during two world wars, Reuters reports.

The incident highlights ongoing safety concerns in South Africa’s mining sector, which has been conducting campaigns under the “Zero Harm” initiative to reduce fatalities and injuries. Last year, the country recorded its lowest-ever number of mine deaths, at 41.