Scientists at Otago University say the PSA kiwifruit disease almost definitely came from China and most likely from imported Chinese pollen.
A team of biochemists is confident it will be able to confirm the source of the disease shortly, after studying its genetic code since the outbreak in November 2010.
The scientists have been able to identify differences between the strains of PSA, with the aid of genomic technology which arrived in New Zealand last year.
They have narrowed the suspects down to two: China and Italy.
Associate professor Russell Poulter says initial results show PSA originated from China.
He says the next step is to establish how it got here.