Thirteen miners were trapped underground at the company’s Masakhane mine west of Johannesburg earlier on Thursday after an earthquake that measured 2.2 caused a cave-in.

Sibanye-Stillwater said two employees were taken to a hospital and were in stable condition, while the remaining two were still being brought to the surface.

Another three employees have been located and are responding to rescue teams, the firm said.

Sibanye-Stillwater “will continue to make every effort to locate the remaining five employees who are unaccounted for, and return all the employees safely to surface,” the company said in an updated statement on Thursday.

South Africa is home to the world’s deepest mines.

More than 1,000 mine workers were rescued after being trapped underground for more than 24 hours after a storm knocked out power lines supplying electricity to Sibanye-Stillwater’s Beatrix gold mine in February.

Sibanye-Stillwater produces more gold in South Africa than any other company. The company also produces platinum and has operations in the United States.