A 15-year-old boy has been referred to Youth Aid following a brawl at a high school rugby match in Otahuhu last month.
Counties Manukau West Area Commander Inspector Jason Hewett said police believe the 15-year-old boy was responsible for throwing a punch that left another 15-year-old boy unconscious.
Mr Hewett said the investigation was lengthy and involved interviewing a large number of people, including adults, who needed to take responsibility for their actions.
"This was a high school rugby match, that sort of behaviour is absolutely unacceptable and will not be tolerated in the community.
"Everyone who attends sport events like this needs to be safe and feel safe while attending."