The Ministry for Primary Industries says an eighth Queensland fruit fly has been found in Auckland.
Larvae had also been found in fruit from an adjoining property to the property where the first fruit fly was found.
The ministry said staff had removed the pieces of fruit, incubated them then found the rice grain sized larvae as they dissected the fruit.
Its chief operating officer Andrew Coleman said the trapping system, which caught males only, continued to prove effective.
He said a single female fly was identified by a Grey Lynn resident last week and today's find brings the number of adults flies found to eight.
Mr Coleman said finding the origin of the latest incursion was challenging, because the Queensland fruit fly could have entered New Zealand via multiple pathways.
He said produce could arrive in the country through various avenues including cargo, mail, cruise ships, or airport passengers.
Mr Coleman said the ministry was looking at making a genetic match between fruit flies trapped here and populations in Australia to determine where they came from.