The poisoning of a row of pohutukawa trees in a bay near Kerikeri has now been referred to the police.
Pohutukawa along the beachfront at Opito Bay have been ailing for some time but it was only in late November that residents discovered the roots were riddled with drill holes.
An arborist who inspected the trees on November 28 determined they had been poisoned and would almost certainly die. At least four trees are affected. A number of dead branches have already been removed.
The attack outraged residents in the small beachside community, many of who are descended from the landowner who planted the trees on what used to be a bleak, shadeless shoreline.
One put up a sign saying "Shame on those who poisoned our trees"; others left flowers.
Far North District Council staff went to door-to-door asking for information and checking whether anyone's home security cameras could have recorded the attack.
It is believed council staff were unable to identify the perpetrator and have now called in the police.
Sergeant Haydn Korach, of Kerikeri police, confirmed a formal complaint had been laid over the suspected poisoning.
A senior constable familiar with the area had been assigned to the case and would be working with the council and local residents in a bid to find out who was responsible.
He urged anyone with information to call Kerikeri police on (09) 407 9211 or Crimestoppers, anonymously, on 0800 555 111.
It is believed the council obtained some security camera footage which has been handed to the police. A police officer inspected the crime scene last Thursday.
If a suspect is found police could lay a charge of wilful damage.
The council could prosecute under the Reserves Act or even the Resource Management Act, which allows for fines of up to $300,000 for killing native trees on public land.