A teenage boy who was injured in an out-of-control south Auckland college rugby match brawl has been discharged from Middlemore Hospital.

Police said 30 to 40 people, including rugby players, family members, and spectators were involved in the brawl during an under-15 match between Otahuhu College and Tangaroa College at Sturges Park in Otahuhu, which took place yesterday.

A 14-year-old Otahuhu player was taken to hospital in serious condition after he was allegedly knocked out by a punch from behind by a Tangaroa supporter.

His condition improved yesterday and he was discharged this morning.

Police said they have spoken with a number of witnesses.

Counties Manukau senior sergeant Jeremy Field said it is unclear whether any charges will be laid.

He said both schools are co-operating with police so far.