The company confirmed the slip occurred yesterday following heavy rain in the area.
The mine site, which consists of an open pit, an underground mine and an adjacent processing plant, is located between Palmerston and Ranfurly.
"At the Macraes open pit operation, located at Macraes Flat, Otago, a section of the west wall failed following heavy rainfall," Oceana Gold said in a statement.
"The wall was being continuously monitored and there were not personnel working in the open pit at the time of the failure. Access to the underground mine was cut off by the failure, but the underground mine itself is unaffected."
All staff who were working underground were brought safely to the surface.
APNZ understand the workers were flown to safety by helicopter, and the mine closed as a result of the slip.
Oceana Gold said it expected "minimal impact" on its short-term production, with stockpiles of ore available for processing.
Worksafe NZ confirmed an investigator was on their way to the mine site today.
Earlier this year, 39 Gough Group employees working at the Macraes mine were laid off as a result of cost-cutting measures at Oceana Gold.
