Kauri dieback disease may have reached trees on Auckland's North Shore.
Auckland Council has closed a track at the Chelsea Estate Heritage Park because of concerns a tree there may be affected with the disease.
Council biosecurity manager Phil Brown said there was a strong possibility the tree had dieback and it may have been in decline for some years.
Soil samples from around the tree had been taken and signs closing the track were being installed, he said.
"The tree is showing signs of decline, however we cannot be 100 percent sure of infection until the test results come back."
The track had been closed as a precautionary measure while the council waited for confirmation and developed a plan to respond.
"From what we know about the incubation period for this disease, if it is in fact infected, this tree may have been in decline for some years yet not necessarily showing any visible signs of infection," Mr Brown said.
The tree was found during the council's track surveys, which have been carried out over the past few months.
Aerial surveys were also done across north Auckland with the Ministry for Primary Industries.
Kauri dieback has already devastated Auckland's Waitākere Ranges, where an estimated 20 percent of trees have been infected in the last five years.
On Wednesday, Auckland Council officially closed all forested areas of the ranges, affecting nearly all of the 172 tracks within the 16,000-hectare area.
It also closed 10 tracks in the Hunua Ranges.
The ministry also issued strict cleaning and monitoring guidelines across the remaining forest and open tracks.
People caught disobeying the rules on an open track face a maximum penalty of three months imprisonment or a $50,000 fine.
For a trespass notice on closed tracks it's a fine of $20,000.
The spores of kauri dieback disease are spread by soil carried on shoes, as well as the feet of animals.