A Pollsmoor Prison inmate was stabbed 21 times during a gang fight, which left nine other inmates injured, the Correctional Services Department said on Friday.
Five offenders were admitted to public hospitals after the fight between the 26 gang and 28 gang members.
"Two of those injured were referred to Victoria Hospital in Wynberg, while another three were referred to Groote Schuur Hospital for treatment," said Western Cape regional commissioner Delekile Klaas.
It was the second fight that had broken out at Pollsmoor this week.
"Before this, another five were injured in a gang fight among members of the 26 gang," said Klaas.
Most of the inmates had been discharged from hospital, with three remaining for treatment.
"One of those still being treated was admitted to the Intensive Care Unit with 21 stab wounds."
Klaas said the situation had been brought under control after members of the department's Emergency Support Team (EST) had been deployed to the jail.
Police were investigating the incidents.
"During our search and seizure operations we confiscated cellphones, chargers, drugs, such as Tik, a DSTV Walka, and dangerous self-made weapons."
Klaas said the ringleaders had been separated from other prisoners and were being held in single cells to prevent a recurrence of the violence.
The EST teams were on high alert, with department managers being recalled from leave to help normalise the situation.
The fights at Pollsmoor follow similar violence that broke out in St Albans Prison in Port Elizabeth and Groenpunt Prison in the Free State this month.
Three prisoners were killed and scores injured in a gang-related fight at St Albans last week.
On 7 January inmates at the Groenpunt facility went on a rampage, torching their cells and offices at the prison.
Four warders and around 50 maximum sentence inmates were injured in the incident.