The Food Safety Authority is investigating the possible illegal use of a banned insecticide, which has shown up in the latest survey of chemical residues in fruit and vegetables.
But the FSA says the residue surveillance programme which tested a range of domestic and imported fresh produce, found no chemical traces at levels that would represent a health risk.
However, the Pesticide Action Network says the results are the worst it's seen.
It says more than 90% of the fruit and vegetables tested contained residues and traces of the insecticide endosulfan were found in cucumbers. Endosulfan was banned in New Zealand two years ago.
The network says it means either domestic growers have been illegally using old stocks of endosulfan, or it was in cucumbers imported from Australia, where its use is still permitted.
The FSA says it is concerned at the possibility the chemical may have been illegally used here.
Principal chemicals adviser Paul Dansted says the agency is not happy either, with higher than permitted levels of two chemicals found in pak choy or bok choy samples; the fungicide chlorothalonil and the insecticide thiamethoxam.
The FSA thinks that might be due to grower confusion over the level of chemical application for different sorts of brassicas.