But parents seemed unaware of how far a social media invitation could spread.
Not much could be done to educate parents about the use of social media to create mass gatherings but party organisers should use the functions available on sites such as Facebook to limit the number of attendees, said Mr Cocker.
"People need to understand the mechanisms of Facebook, there are ways to contain the invite."
Another option was The Party Registration Scheme, which allowed individuals and businesses to register their party or event with the police.
RoadSafe Hawke's Bay regional manager Linda Anderson said it had two or three parties registered each week from a broad range of age groups.
Police were able to run safety checks on the event in the course of their patrols.
Visit www.partyregisterhb.co.nz for more information.