JOHANNESBURG (Reuters) - Hundreds of South African gold mine workers were rescued and over 100 treated for smoke inhalation after an underground fire, the National Union of Mineworkers (NUM) said on Thursday.

Safety is a huge issue in South Africa’s dangerous deep-level mines and a focus for investors. A spate of deaths at Sibanye-Stillwater’s gold operations, including a seismic event that killed seven miners in early May, has highlighted the risks.

In the latest incident, more than 600 miners were initially trapped after a fire broke out at a mine east of Johannesburg operated by unlisted Gold One, NUM said.

This comes almost two weeks after five miners died in an underground fire at a South African copper mine operated by unlisted Palabora Mining Company in Limpopo.

Company officials could not immediately be reached for comment.

“As the NUM, we vehemently condemn this kind of incident as it is becoming a trend,” the union said in a statement.