A witness to an incident circulating on social media which shows a police officer shoving a teenager off his bike says he thinks the police overreacted.
A video of the incident in south Auckland has been put up on Facebook and viewed more than 37,000 times.
Police said they had received several calls from members of the public on Saturday evening, complaining about a group of teenagers making excessive noise, fighting and weaving in and out of traffic on bikes.
Brandon Pelega Eliu, 14, said he was riding his bike alongside nine others when a police car drove past.
He said an officer yelled at them to go home and then rammed into one of them riding up ahead.
"And the boy on the bike went to ride away from the police officer, and the officer told him to stop.
"And then he picked him and threw him off his bike, and then picked him up again and threw him against the fence."
Brandon said the teenager was then taken away in the patrol car.
Police said they had concerns about what could be seen in the video.
They said they have opened an investigation into the incident, and would not comment specifically on any claims.