Inspecting Judge of Prisons Nathan Erasmus yesterday began a 48-hour inspection of the "notorious" Waterval Prison outside Newcastle, in northern KwaZulu-Natal.
The probe has been prompted by recent deaths of inmates at the prison.
Two prisoners died during violence among inmates at the prison in March while warders allegedly stood by fuelling the fighting.
One of the prisoners, Thamsanqa Dladla, 27, from Inanda, north of Durban, was due to be released two weeks before his death. His family was allegedly informed of his demise seven days after his death.
Six inmates have died at the prison since December last year. Erasmus said yesterday that he would investigate all the issues raised.
"I'm here for two days to interact with inmates. I have ordered them to provide us with all the information in black and white. We'll keep it confidential."