Police have charged four men in connection with gang-related stabbings at Auckland Prison at Paremoremo.
Three men were injured in the fight earlier this month, two of them stabbed.
Police have been reviewing security footage and interviewing staff who were working at the time, and have said the victims as well as the possible attackers have been refusing to talk about what happened.
The four men - aged 21, 22, 33 and 37 - now face charges including wounding with intent to cause grievous bodily harm and injuring with intent to cause grievous bodily harm.
All four are due to appear in the North Shore District Court next Monday.