Forest research institute Scion has confirmed it will continue its genetically engineered tree trial and will replace hundreds of genetically modified pines destroyed last month, while police continue to investigate the attack.
375 young trees were cut down or pulled from the ground when the heavily protected trial site in Rotorua was broken into during Easter.
The trees were part of a project to study herbicide resistance and reproductive development in genetically engineered pines.
Scion chief executive Dr Warren Parker says the research is important to the forest industry and the institute has decided the field trial should continue, but under even tighter security.
Dr Parker says the cost of replacing the destroyed trees, extra security and lost time, will add up to about $1 million.
But he says Scion will be able to replant the site this winter.
Dr Parker says police are following some leads and he says it is likely that more than one person was involved in the attack.