By RNZ

There have still been no arrests after three teenagers were stabbed at a Christchurch party, with one losing their life.

Zion Purukamu, 16, died from his injuries while the other two victims remained in hospital in a serious but stable condition.

Medbury Tce in Fendalton remained cordoned off as police continued to hunt for clues.

Officers in boiler suits, some using metal detectors, had been gathering evidence from the home where the party was, a parked car and neighbouring properties.

Danielle Anderson and Freddie Gash were returning to their student flat on Friday night just after the stabbings.

"We pulled around the corner and saw the police cars. There were two young kids in the back maybe being taken home. And there was another young girl who was just kind of throwing her arms up and looked quite upset at the cops."

Police said 80 guests ended up at the gathering at the rented Airbnb home, including a number who weren't invited.

Anderson was taken aback by the age of those injured.

"That's such a young group of people. Like, I can't believe that they've done that."

Gash said being close to the university, they sometimes got student parties that got out of hand, but this was something quite different.

"Not down this street, I mean it's right opposite the private school... I was very surprised and sort of shocked really to hear that that had gone on."

Ying Kuang lives close by and was woken by people shouting.

He said he heard the noise and yelling about 11.10pm, and saw ambulances and police.

Kuang's thoughts went out to Purukamu's family and those of the two injured teens.

"I feel very sad, and I feel I can't believe it has happened to teenagers. They are so young."

Long time Christchurch youth advocate Dame Sue Bagshaw said teenagers throwing parties needed to plan for the possibility that uninvited guests might turn up.

"Everybody assumes it's going to go well, we don't need to worry about it. We'll have fun and that's all we have to do. But I think you have to plan that it might get out of hand and you have to plan for that. So what will happen if you get get crashes, what are you going to do?"

And she had this advice for parents with teenagers.

"The most important thing is for parents to keep listening to their kids. Keep talking to them."

Dame Sue said parents who were worried their children wouldn't listen to them could always bring a youth worker on board to get alongside their teens and help them plan a safe gathering.