Over the weekend police swooped to arrest four more people in connection with the pre-arranged fight.
The men, aged 28, 18 and 16 from Sunderland and 15-year-old boy from Chester-le-Street were released on bail after questioning.
This brings the total number of people arrested to 19.
The fight happened at around 2.15pm on Saturday, January 12.
Police are still circulating CCTV stills of eight men they want to trace.