Ancient swamp kauri exported to China to meet demand.
Thousands of tonnes of kauri are being hauled off to China, firing concerns New Zealand is being stripped of a national treasure.
The "black gold rush" - as it is known in Northland - is trying to meet Chinese demand for the ancient wood.
Under the Forests Act, it is illegal to export any swamp kauri unless it is a finished product or a personal effect, or it is from stump or root material (either whole or sawn) sourced from non-indigenous forest land.
A Ministry for Primary Industries spokeswoman said export approval had been declined for consignments which failed to comply but no one had yet been prosecuted for criminal breaches of the provisions.
Some Northlanders see it as the loss of a national treasure.
Northland Regional Council operations director Tony Phipps said: "You hear that people are doing all sorts of cunning things to try and get around export requirements."
According to the Ministry for Primary Industries, nearly 600cu m has been exported in the past two years.
On Wednesday, Chinese investors flew into Mangawhai to inspect an extremely rare 48,000-year-old kauri log unearthed from farmland.
Farm owner Bruce Tucker said the log would earn him more than $25,000 - 40 per cent of the eventual sale price - and he was told it was for the Beijing World Art Museum.
Tucker discovered the swamp kauri while putting in a road a month ago at his 32ha farm.
An extraction team, from Swamp Loggers, have pulled out stumps of various sizes and Tucker was hopeful they could find several hundred thousand dollars worth of kauri, which would fetch $400 to $600 per cu m.
"We have already found 1000cu m and have only dug up a quarter of the farm," he said.
One Swamp Loggers worker, who spoke on condition of anonymity, said: "Everyone is just trying to make money out of it but it's the same old thing, it's not easy. All the wood that was easily extractable has gone."
Another kauri extractor, Gary Beckham, said he was trying to find four massive logs - 2m in diameter and 4m in length - to meet an order from South Korea for a peace monument on its border with North Korea.
Beckham is one of several kauri extractors facing prosecution for removing kauri from protected wetlands.
Green Party primary industries spokesman Steffan Browning said the issue of swamp kauri exports needed urgent attention.
"I think they could be a lot more careful about protecting what is a finite resource."
Neil Fraser, managing director at Kauri Clock Factory in Whangarei, said: "It's a limited resource and we are chucking it in a container and sending it overseas.
"It's the oldest workable timber in the world, you just don't get it anywhere else in the world. Once it's gone, it's gone. You are never going to get it back."