Efforts to track down the varroa mite in beehives around Murchison, 130km southwest of Nelson, are to be intensified.
The Ministry of Agriculture and Forestry varroa programme co-ordinator, Paul Bolger, said testing would be scaled up to a 5km radius around the site where a questionable varroa sample was taken.
He saidit was still a precautionary measure at this stage, but he accepted that the original sample was "probably" caused by cross-contamination in the testing laboratory.
Meanwhile, testing of 4000 hive samples in the Oxford and Murchison areas has found no further varroa presence.
