File picture: Cao Yang, Xinhua News Agency

Johannesburg - The National Union of Mineworkers (NUM) said on Thursday, that it has been informed that six workers are trapped underground at AngloGold Ashanti's Mponeng mine near Carletonville, west of Johannesburg, as a result of fall of the ground. 

The Mponeng mine is 3.8km deep.

"This fall of ground was triggered by a seismic event of 1.1 magnitudes that took place at around 10am this morning. This is the third incident since last month," Erick Gcilitshana, NUM's health and safety secretary said.

"The search team is able to communicate with one worker. The rescue operation has started. The NUM wishes all six workers to be rescued alive."

AngloGold Ashanti and Mine Rescue Services were not immediately available for comment.

In September, AngloGold was awarded South Africa’s most prestigious safety accolade at the annual MineSAFE Conference, for the mining company with the best safety improvements, achieved at its ultra-deep mines. 

Last month, two earth tremors that happened 3.7km deep killed one miner and injured two others at the same mine.

In August, five workers were killed in a seismic event at Harmony Gold's Kusasalethu mine also in the Carletonville area.