The protest action began on Monday morning, Impala said in a statement.
"As at 15h00 (1300 GMT), approximately 2,205 employees were still underground, with the motivation and demands of the protest still to be determined," Impala said.
This is the latest in a spate of underground sit-ins at South African mines. Over the past two months, similar protests have been reported at Wesizwe Platinum's Bakubung operations and the privately owned Gold One Group's Modder East mine over wage and representation demands.
The National Union of Mineworkers (NUM), the majority union at the Bafokeng mine, was not immediately available to comment. In 2019, NUM signed a five-year wage deal with Royal Bafokeng Platinum, the mine's previous owners, which is due to lapse next year.
Impala took control of Royal Bafokeng Platinum in July after a lengthy takeover battle with Northam Platinum, securing huge, high-grade assets that are vital to its future growth.
South Africa's platinum miners, including Impala and Sibanye Stillwater are in the process of cutting jobs as they battle to stay afloat in the face of weak metal prices.
Impala said rising cases of illegal industrial action "pose a risk to sustainable employment, particularly given the low metal price environment currently facing PGM producers".
The miner recently suffered a major accident at its Rustenburg operations when a hoist that carries workers up and down an underground shaft malfunctioned, killing 13 workers and injuring scores of others.
(Reporting by Nelson Banya; Editing by Andrea Ricci)
By Nelson Banya
