Johannesburg - Impala Platinum (Implats) said on Wednesday that two workers were missing after a shaft collapsed at its Rustenburg mine.
Operations at the shaft were suspended when the shaft collapsed on Tuesday, trapping nine workers underground before seven were rescued.
Implats' investor relations officer Alice Lourens said the company - the world's second-biggest platinum producer - was trying to find the missing workers.
The cause of the collapse at the mine had not yet been established, the company said.
Four employees were killed at one of Implats' Rustenburg shafts following a fire in January.