A teenager was critically ill in hospital last night following a street brawl involving about 50 youths in the Auckland inner-city suburb of Grey Lynn.

The 17-year-old youth suffered multiple injuries in the fight, which erupted about 3.30am yesterday near a party attended by hundreds of young people at an abandoned warehouse.

Detective Inspector Bernie Hollewand described the party as an after-ball bash for Auckland Girls Grammar School students.

The school ball was held at an Auckland hotel on Saturday night but board of trustees chairwoman Ann Northover said there was no official after-ball function.

"There may have been some Auckland Girls' [students at the warehouse] but it was nothing associated with the school [or] organised by the school."

Mr Hollewand said the injured youth was a student but he would not identify his school.

"Some reports put the people out on the streets alone at 50, and then there are the people coming and going congregating around the door of that function."

Police cordoned off part of Surrey Cres and adjoining Browning St and spent most of yesterday combing the area for evidence. Officers were seen dusting post boxes and light posts, and spent time going through a rubbish skip outside a house.

Police inspected freshly painted graffiti near the warehouse and visited a property known for having regular parties, residents said.

A woman living outside the police cordon said she had seen a young man stopped by police. He lifted his shirt and the officer appeared to check his body for injuries, she said.

The Rev Hugh Kempster of St Columba Church, near the party scene, said police were twice called to the area early yesterday.

He rang them at 1am after "hearing a bit of a racket" in the street and seeing a "stream of kids going down the road".

Another resident told him they had phoned police at 2.30am.

He understood that news of the party was supposed to be kept quiet but word spread by text message and 400 to 500 people turned up.

The brawl followed a spate of disorderly behaviour and vandalism from a small gang of youths, he said.

Mr Kempster said that last Thursday night, a brick had been thrown through one of the church's leadlight windows, and the following night a tree was damaged.

"Our guess - it's obviously total speculation - is there has been a gang hanging around the Surrey Cres area for the last few nights getting blasted and that, combined with the ball - 400 tanked-up kids - just turned into a volatile mix," said Mr Kempster.

Mr Hollewand would not say whether weapons were involved in the fight.

No one has been charged.