There has been a shock find of the devastating plant disease banana freckle almost a hundred kilometres from the initial outbreak zone in the Northern Territory.
The surprise case, the NT's 13th, was discovered on a government research farm.
It is the first confirmed case outside the outbreak area.
Before Friday's unwanted surprise, biosecurity officials had hoped they had the outbreak contained to the Batchelor-Rum Jungle region, about 100km to the south of Darwin.
There are now 12 infected properties in the Batchelor area.
On Friday afternoon, banana freckle was confirmed at the government's own research facility, believed to be the Beatrice Hill Research Farm at Middle Point.
Officials said the case was confirmed on a single leaf on a single plant in a secure area of the research farm.
Extra testing is underway on banana trees surrounding the infected plant.
All banana trees at the site are being destroyed and disposed of on the property.
NT chief plant health officer, Dr Anne Walters said: "We're currently investigating how this case of banana freckle has emerged at a secure government research facility, and are urging people to be vigilant for the disease which is spread by wind and rain.
Federal authorities are working on a containment plan.
Before this latest find, the official biosecurity position was that the outbreak is "still technically feasible to eradicate".
Officials are keen to prevent the devastating response which following the last outbreak in 2013.
That outbreak resulted in a Territory-wide destruction of all banana plants in the biggest plant disease response ever seen in Australia.
Questions are now being asked on whether the decision to declare the NT free of the devastating disease in 2019 was premature.
Since the first cases were confirmed early in June, biosecurity officials have been sweeping the surrounding district checking on other plants.
Banana freckle is a fungal disease of banana leaves and fruit.
Owners of the 12 infected properties have been told they are not allowed to move plant products, material or equipment from the property.
Suspect samples from four other properties in the Batchelor-Rum Jungle region are underway.
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Surveillance is continuing to determine the extent of the outbreak, with more than 130 properties examined so far.
The NT Industry, Tourism and Trade Department said plant biosecurity officers are following strict biosecurity decontamination protocols when entering and exiting any premises to prevent the risk of spreading the disease.
NT chief plant health officer, Dr Anne Walters said members of the public had been supplying photographs of unusual signs on their plants to help chart the outbreak.
"Banana freckle is a serious threat to the industry," she said.
"It decreases plant health and productivity by reducing the amount of healthy leaf area, and affects fruit quality and appearance, even though the fruit are still safe to eat."
NT Farmers chief executive Paul Burke said growers were being supported "to ensure the best outcome for all parties involved during this difficult time".
He said farmers urged anyone with banana plants which don't appear to be normal to call the Exotic Plant Pest Hotline on 1800 084 881.
Quarantine restrictions have been established to stop bananas or banana plants leaving the Territory.
Officials have stated the current outbreak was not connected to the 2013 outbreak which cost almost $30 million to clean up.
Back then 43,589 properties were involved in a NT-wide surveillance program with more than 500,000 banana plants destroyed on 9500 properties.
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