Underage drinkers at a 200 strong party turned nasty after being confronted by police.
Nine arrests were made at the party on Auckland's North Shore earlier this month.
The council owned venue, in central Takapuna, was hired on the agreement there would be no alcohol on site.
"Police were confronted with up to 200 intoxicated persons, many underage who turned on police," police said in a statement.
"Nine people were arrested and areas of the Takapuna CBD shut down for over an hour as police attempted to return order."
Alcohol consumption by under 18s at the pre-planned event has sparked a police and council investigation with charges likely under the Sale of Liquor Act.
Police have used the illegal party as an opportunity to remind parents and caregivers of their legal responsibilities when hosting events.
"Remember you are responsible for not only your own child, but the welfare of every other child or young person that attends that event."
Alcohol basics from NZ Police:
• Parents or guardians:
• Need to be responsible for how much under 18s drink.
• Supervising amount and what they drink.
• Make sure under 18s don't drink too much, that they do eat food, drink water and are physically and emotionally safe.
• Being upstairs watching movies or drinking with your own friends is not considered supervising or being responsible.
• If, as a parent or guardian, you are happy for your under 18 to go to a party with alcohol then you need to give permission to the adult who is going to be responsible and in charge of your child at that party.
• Speaking directly to that person and asking questions is a good indication as to the type of party you are allowing them to attend.
• As an adult, if you organise a party for your under 18 or have under 18s attending a party you are having, you can be charged if that party becomes out of control and under 18s are located drunk.
• As the adult at the party it does not matter if the under 18s brought their own alcohol or you gave it to them, you can still be charged.
• Supplying alcohol to under 18s who are not your own is an offence.
• Being in charge at a party where under 18s are drinking to excess is an offence.