Police in Christchurch arrested four Canterbury University students on Wednesday night after being pelted with bottles at a party they describe as riotous.
Inspector Malcolm Johnston says says a drunken crowd of more than 250 people gathered at a house in the suburb of Riccarton.
He says the party, an unofficial function following a university boardriders association event, was the most disorderly police have attended for some time.
Inspector Johnston described the students' behaviour as rioting and says they also lit a large bonfire, jumped on neighbours' cars, trespassed through surrounding properties and knocked over wheelie bins.
The arrested students were released with a warning.
Fifteen police officers went to the house at 11pm on Wednesday, following complaints about the noise.
Inspector Johnston says the police are talking to the university in an effort to identify repeat offenders and avoid similar situations happening again.