MPI deputy director of general regulation and assurance Scott Gallacher said it had been working to locate the source of the outbreak, but the information was preliminary and far from conclusive.
"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 supermarket chain."
The ESR reports had provided useful pointers for the ministry's investigation, Mr Gallacher said.
A survey involving 96 people affected by the illness revealed that 87 had purchased lettuce, however only 17 respondents identified any of the brands asked about in the survey, he said.
The outbreak of the stomach complaint peaked in mid-September, Mr Gallacher said.
There was no single food that had been consumed by 100 per cent of those who have fallen ill with the bug, the ministry said.
Foodstuffs today confirmed two of its products - Pams Fresh Mesclun Salad Lettuce and Pams Fresh Express Lettuce - were named in one of the ESR reports.
The products were traced back to three farm paddocks but were now past their use-by dates and no longer on shelves. Remaining Pams bagged lettuce products were safe for normal consumption, the company said.
Foodstuffs was now also undertaking its own independent audit and was confirming its farms were free from any possible contaminants prior to replanting.
This evening, Mr Gallacher told APNZ that carrots and lettuce remained the key culprits and confirmed that no non-fresh items were mentioned in the ESR report.
He said although Foodstuffs confirmed two of its Pams products were mentioned in the ESR report, they were only identified as being consumed by eight of the 96 survey respondents.
"ESR themselves acknowledged that there's not a lot of definitive stuff. We still need to investigate this further."
The ESR report would be released "in the next week or so", Mr Gallacher said.
"We're not the authors and we don't actually own the reports so we need to work with the Ministry of Health [who commissioned the report].
"If we can get them out sooner, they'll be coming out sooner and that's what I would like."
There had been no new confirmed cases since September 30, Mr Gallacher added.
Labour's food safety spokesman Damien O'Connor said the ministry must name all the products in the ESR report.
"MPI either lacks the resources or is incapable of dealing with what should be a relatively minor food safety issue. This will be a concern to our export sectors.
"It also reinforces Labour's call for New Zealand to return to a stand-alone food safety agency."
MPI continued to advise normal food safety practice, including washing fruit and vegetables before eating.
Those who believed they might have symptoms were advised to see their doctor, or call Healthline on 0800 611 116 for advice.
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