Food Safety Minister Jo Goodhew says she is satisfied with the way the Ministry for Primary Industries handled the recent outbreak of a severe gastro bug.
About 170 people contracted Yersinia pseudotuberculosis in September and October from what is thought to be bagged lettuce and carrots, and 72 people needed hospital treatment.
Documents released under the Official Information Act show a report by the Institute of Environmental Science and Research (ESR) on 6 October named bagged lettuce and carrots as the likely source of the bacteria.
A scan of a group of Yersinia pseudotuberculosis bacteria Photo: SCIENCE PHOTO LIBRARY
But officials at the Ministry for Primary Industries (MPI) did not release the information as they did not want to panic the public.
Ms Goodhew said MPI got the balance right.
"The balance is, that we could have gone out and said 'this could potentially be meat products, dairy products, fruit or vegetables' and that would have panicked the public. Once we saw the ESR report, even then, we knew the general public had eaten carrots and lettuce a lot of the time too."
Canterbury Medical Officer of Health Dr Alistair Humphrey said it was impossible to know whether fewer people would have got the bug if MPI had made the public aware of the probable cause of the outbreak .
Dr Alistair Humphrey named the vegetables in October, against MPI's advice, but not the brand.
He said it was difficult to know whether MPI's actions caused more people to get sick.
"Whether MPI's action caused some people not to get rid of old carrots and lettuce and therefore become ill is very difficult to say, although there have been a number of cases through October."