The source of a nasty gastro-intestinal outbreak is still under investigation after five cases were reported in the Bay of Plenty.

Ministry of Primary Industries general regulation and assurance deputy director Scott Gallacher says incomplete and preliminary information was released to the media last week, which has fuelled speculation.

Five cases of the gastro bug were reported in the Bay of Plenty.

He says: 'While the investigation has not yet identified the source, it's important to stop the speculation as to what foods are being investigated.”

Scott says MPI is continuing to seek to identify the origins of the outbreak, drawing upon the best available expertise and information, both domestically and internationally.

Food safety is the MPI's highest priority in relation to the outbreak of illness caused by Yersinia pseudotuberculosis.

'The health data is telling us we are dealing with a contamination event that happened in August,” he adds. 'This was identified as an outbreak of illness on 23 September.

'According to the latest health data, there have been no further confirmed cases since the first week of October.”

MPI has released the case-control studies, commissioned by the Ministry of Health and produced by the Institute of Environment and Science and Research, to identify foods for further investigation in locating the source of this outbreak.

'The case-control studies were produced by scientists for specialists conducting a food safety investigation,” adds Scott.

He says the case-control studies from ESR identify a range of foods that need further investigation to establish if they are the source of this illness.

He says they do not provide a definitive list of affected foods.

Scott says: 'In the case of lettuce, which is identified as a food to investigate, there are numerous varieties of whole lettuce, leaves, leaves of mixed varieties and premixed salads covered by many brands.

'Lettuce is a very commonly consumed food, which was consumed throughout this outbreak with the vast majority of consumers not becoming ill.

'Most of the patients surveyed remembered eating some kind of lettuce, with eight out of 96 remembering one brand, but the vast majority of those surveyed could not specify the type or brand of product.

'We are getting a lot of information, building a picture and investigating many avenues.

'It is not a simple situation where we can recall a single product. It is not definitively linked to any one producer, distributor, wholesaler or retailer.

'MPI has been checking with major food suppliers to ensure the food handling practices are meeting the required standard.”