Four suspected illegal miners were found shot dead at an old mine shaft in Benoni, on the East Rand, Gauteng police said on Thursday.
"We just got to the scene and discovered four bodies. Three others were injured and are under police guard in hospital," said spokesperson Captain Tsekiso Mofokeng.
The incident was suspected to have happened overnight, he said.
"We suspect that one of the illegal miners called the police and alerted them about the incident. An investigation has been launched."