Vandals cut through a 2.4m high security fence, dug a metre to cut through another security fence and made their way under a third, electrified, fence at Scion to destroy hundreds of genetically modified trees growing in a field trial.
All 375 radiata pine trees, planted last year as part of an approved field trial, were either pulled out by the roots or cut at the base.
Police believe the vandals broke in sometime on Monday or early Tuesday.
Scion chief executive Dr Warren Parker described the destruction as a blatant act of vandalism aimed at halting Scion's genetic modification programme.
The cost of the damage was around $400,000 but could be as high as $1 million with the trial to start again and more security to be looked at as well as lost research time.
"It's just wasteful. No doubt it has set us back up to a year," he said.
"The field trial was approved under one of the strictest regulatory regimes in the world and our team has fully complied with the containment controls. Despite this, our research opponents were determined to stop us and used criminal means to do so," he said.
This is the second time the Crown forestry research institute's field trials have been vandalised by protesters. In January 2008, 19 trees were cut down by vandals digging under the perimeter fence. They left behind a spade with a sticker saying "GE Free New Zealand".
This time the vandals destroyed many more trees set inside the 1ha field trial site.
The area is secured by a double fence, one of which is electrified and monitored.
The offenders had cut through a perimeter fence to get to the secure area.
Not all the trees destroyed were genetically modified.
They were part of two experiments due to run for two to three years, testing herbicide resistance and reproductive development.
Scion is revisiting security around the site following the breach so the work can continue.
Some of the misconceptions surrounding genetic modification included that it was dangerous and at risk of getting into the food chain, but these were unfounded and unnecessary concerns, Dr Parker said.
"Some people think it is dangerous and Frankenstein and so forth ... all of the genes involved are natural not animal or human ... it's safe. There is no way it could get into the food chain.
"This was just the wanton actions of an individual," he said.
Research being undertaken by scientists at Scion was beneficial to New Zealand forestry economically and environmentally, he said.
The actions of the vandals involved wouldn't put them off supporting the scientists in their work.
Dr Parker said they had some genetically modified trees in a separate containment area which would be used to ensure the programme continued.
"This was a big blow to us ... we will not be deterred from going about our lawful research. New Zealand needs to benefit from this research," he said.
GE Free NZ president Claire Bleakley said she was "highly shocked" to hear of the vandalism.
As it was the second breach at the research centre, GM trials needed to be halted there, Mrs Bleakley said.
"This should signal the end of GE trials at this facility.
"This breach has occurred exactly the same way before. It's a waste of taxpayer money," she said.
She fears some of the trees have been taken out of the containment area, which would have the potential to endanger future forestry in the area.
"It could have economic repercussions for the likes of forestry which we depend on," she said.
Police are investigating the incident. If you saw anything suspicious in the area on Easter Monday or early Tuesday or know who may be responsible, call Rotorua police on (07) 348 0099 or (freephone) 0800 555111.