Impala Platinum has confirmed 11 workers died in an incident at one of its mining shafts in Rustenburg, South African broadcaster eNCA reported, citing the company’s spokesperson Johan Theron, Report informs via Reuters.

The company said 88 workers were involved in the incident at its No. 11 shaft platinum mining shaft and 77 have been rescued, Theron told eNCA.

The Johannesburg-based platinum miner said in a statement late Monday that it was carrying out rescue efforts after an incident involving its conveyance system, which hoists workers up and down the underground shaft.