Two people are in hospital with fractured skulls after large scale disorder erupted at a series of parties in Rotorua over the weekend.
An open invite on Facebook has been implicated in attracting scores of young people to one of the parties on Friday night.
Police were called to a fight in Pretoria St and King St about 11.20pm and found a series of parties in the same Pretoria St flat complex.
Police said it appeared at least one of the parties was advertised on Facebook as an open invite. Police estimated the parties attracted between 100 and 150 people in their late teens to early 20s.
At least six people were injured as a result of the disorder. All six were taken to hospital and two remain in Waikato Hospital with fractured skulls. Of the other four, one suffered a serious facial laceration requiring numerous stitches and another suffered a "nasty'' head injury.
Police want to hear from anyone in the area who witnessed any assaults, or has information about anyone who was armed or using objects as weapons.
Police also want to know about any other assault victims injured during the disorder.
Anyone with information should contact Rotorua police on (07) 349 9400. Alternatively information can be provided anonymously via Crimestoppers on 0800 555111.