The police investigating the death of a teenager in South Auckland this week, have carried out a number of search warrants.
Fourteen-year-old John Hapeta suffered blunt-force trauma to his head outside his home during birthday celebrations on Tuesday.
Items seized in the searches on Thursday have been sent to Environmental Science and Research for analysis.
About six people have been interviewed after the police received information from the public, and an area canvas will continue over the weekend.
Detective Inspector John Tims says the net is closing on the killer or killers, and an arrest will be made at some stage.
John Hapeta's body is being returned to his family on Friday.
Descriptions have been issued of two men seen running from the scene. Both are Maori who were wearing black hoodies.
The incident in Weymouth was the latest in a series of killings in South Auckland:
Navtej Singh was fatally shot during a robbery at his liquor store in Manurewa on 7 June.
Yan Ping Yang, 80, was beaten unconscious in her Manurewa home on 11 June and died three days later.
Business owner Joanne Wang, 39, died of head injuries after being hit by a car at Westfield Shopping Centre in Manukau on 16 June as she tried to stop a man driving away with her stolen handbag.