Five people were missing on Tuesday after part of the ground collapsed nearly 3,000 metres (10,000 feet) below the surface at one of the world's deepest gold mines in South Africa, the company said.
AngloGold Ashanti said no contact had been made so far with the five employees, whose identities have yet to be released, after the accident on Monday afternoon at the TauTona mine, west of Johannesburg.
The damage, whose exact cause has yet to be determined, took place on a production panel some 2.7 kilometres (1.67 miles) metres below the surface.
The company said the damage was caused by two "seismic events" approximately 25 minutes apart of 1.9 and 2.3 magnitude.
Two employees were rescued immediately after the accident. One suffered minor injuries and the second sustained back injuries and is in a stable condition in hospital.
"Rescue teams are working to rescue the missing employees. There are paramedics at the scene, and medical teams are on standby at the mine's hospital," a company statement said.
"Given the difficult ground conditions in the area of the incident, it is not possible to estimate now how long this operation is likely to take or to speculate on the condition of the men."
The TauTona mine, near the town of Carletonville, began operating in 1962 and is 3.5 kilometres deep. The journey to the rock face can take up to an hour from surface level.