The police and prison union, Popcru, suspect the attack on three prison warders could be a revenge attack by members of the 28s for the death of a gang member during clashes with guards about three years ago.
The warders were stabbed by two inmates at the Eastern Cape's St Alban's Prison on Wednesday morning.
Popcru's Eastern Cape secretary, Xolani Prusente, said the attack may be linked to the violent clashes on 30 August 2019 during which a guard was stabbed in the neck and an inmate was killed at the Gqeberha prison.