Witnesses to a fatal hit and run in the Far North are not cooperating, police say.
Police have been investigating the death of Jahkani Hamilton, 18, who died on Ngapipito Rd near Kaikohe on May 5.
Hamilton was found dead shortly after 11pm and had been knocked off a dirt bike, police said.
An associate of Hamilton was found nearby with serious injuries after also being knocked off a dirt bike.
Police began Operation Concert that night, Detective Senior Sergeant Christan Fouhy said.
Fouhy said the investigation was being hindered by witnesses and their supporters who were choosing to say nothing and actively resisting the investigation.
"This is incredibly frustrating for our team, who are working to seek answers on behalf of a grieving whānau."
There were people in the Mid North community who knew what happened that night, Fouhy said, but were choosing to remain silent.
"No matter what's happened, a young person has lost their life and people need to start talking.
"Misleading police or concealing evidence is a criminal offence, and taking part in this may mean you find yourself being prosecuted."
Police continued to appeal for anyone with information to come forward and speak with the investigation team.
"Our investigation won't be going away.
"Police are committed to finding answers for Jahkani's whānau and I acknowledge the patience they have shown in this investigation."
Anyone who could help police should call 105 using the reference number 260506/1270.
Anyone who wished to provide information anonymously could call Crime Stoppers on 0800 555 111.
