KEY POINTS:
Biosecurity New Zealand has launched an investigation into how tests on 10 horses were cross-contaminated, resulting in positive identification for equine influenza last week.
The horses were imported from the United States on March 23 after testing negative for the disease - but they tested positive five days after arrival in New Zealand, with the results becoming available at the end of March.
The site where the horses were being quarantined was locked down as a precaution on Friday, with no horses allowed to leave or enter the site, and no visitors allowed.
All restrictions placed on the Karaka facility have been lifted and the horses will be cleared for release later today, after a second round of testing today confirmed the horses were free from equine influenza.
Animal imports team manager Rachelle Linwood said Biosecurity New Zealand had completed a second round of tests, and retested the original samples.
"We are now certain that the initial positive result was due to contamination in the laboratory.
"While we are very pleased that all samples have now tested negative, it's disappointing that cross-contamination occurred," Dr Linwood said.
MAF's import standards group manager, Clive Gower-Collins, said earlier that it took very little to skew the results on such a sensitive test - "we may have had contamination from somebody with a cold in the lab".
Dr Linwood said an initial finding from the investigation to ascertain how the tests became contaminated was expected by the end of the week.
Findings would be used to identify ways to reduce the likelihood of cross-contamination occurring in the future.
The test results were crucial because an equine influenza outbreak would put at risk New Zealand's place as the only significant horse-racing nation free of equine flu.
Australia has just wrapped up an inquiry into its own billion-dollar outbreak last year when equine influenza first detected in August spread quickly among horses in New South Wales and Queensland states.
Horse movements were stopped, and some Australian racing halted at a cost estimated at A$1 billion ($1.17 million).
- NZPA
