Maistry added that both inmates were injured during the incident.
An investigation is expected to shed light on whether the inmate died as a result of wounds sustained during the fracas with the fellow inmate, or whether it was from wounds sustained when correctional officers intervened.
He said the matter has been reported to the relevant authorities and the investigation is currently under way.
"DCS conveys condolences to the family of the deceased."
Miles Bhudu, of the South African Prisoners Organisation for Human Rights (SAPOHR), alleged that the deceased was a member of one of the numbers gangs and had purchased nyoape from a non-gang inmate on Sunday.
Later, on Sunday evening, when he and members of his gang were about to smoke the nyoape, they discovered that it was substandard.
The deceased was berated by generals of the gang and "had to retaliate against the non-gang member for selling the substandard nyoape", according to Bhudu.
READ | 'All escapees' from Malmesbury correctional facility rearrested - justice department
"He did it the following morning by stabbing the non-gang member, and he was attacked by the bouncers."
Bhudu was referring to the correctional officers who work as part of the emergency support teams (EST).
He further alleged the inmate died as a result of the intervention by correctional officers. He alleged that they brutally assaulted the prisoner.
SAPOHR condemned what they termed as excessive force used against the deceased, as well as the fact that the deceased allegedly tried to stab a fellow inmate.
Bhudu called on DCS to investigate the matter and for those who are found to be responsible for the death to be brought to book.