This follows the possible link between recent cases of salmonella typhimurium phage type 42 and some brands of flour.
New Zealand Food Safety Authority compliance and investigation director Geoff Allen said this week it was believed the contamination occurred when wheat was being stored before it was made into flour.
The grain may have been exposed to birds.
It was too early to identify where that occurred, as there were between 400 and 900 wheat suppliers in the country.
Mr Allen said licking the spoon during cooking preparations also often exposed people to other raw substances which could contain harmful bacteria, such as raw eggs.
It is hoped that now the flour has been withdrawn for sale, cases of the salmonella, which has affected at least 15 people in Otago and Southland, will drop dramatically.
About 50 cases of salmonella typhimurium phage type 42 have been identified since October 13, mainly in the South Island.
In Otago and Southland, the most recent case was on December 18, Public Health South medical officer of health Dr Marion Poore said.
Health authorities became concerned about the increase in this strain of salmonella, as last year only 15 cases were recorded across the whole of the country, with 28 the year before.
While the ages of those affected in the recent outbreak have ranged from 1-86, the illness was seen most commonly in 1 to 4-year-olds.
The next most affected group was 30 to 39-year-olds.
Dr Poore said the vast majority of the adults were women.
While the salmonella bacteria is killed by cooking, it is thought people who may have become sick could have eaten raw cooking mixtures or batter or contacted the bacteria through home-made play dough.
Dunedin mother-of-two Leah Craigie, who became so dehydrated after severe diarrhoea and vomiting that she required intravenous fluids in hospital, said she found the initial findings about flour "really interesting".
She does make uncooked play dough for use at home and believes that is where she may have come into contact with the bacteria.
She said she planned, in future, to make the cooked variety.
Dr Poore said information had been sent to Otago and Southland early childhood centres advising them of the situation.
The difficulty for many people would be knowing whether their flour was one of the batches concerned, as often people tipped flour into another container and discarded packaging.
The advice was that there was no cause for concern as long as the flour was cooked to destroy the bacteria.
Dr Poore said during the festive season when people often gathered in larger than usual groups to share food, it was important to remember the four Cs of good food handling: clean, cook, cover, chill.
The brands of flour which could be contaminated are: Champion, Edmonds, Homelife and Pam's brand plain flours with best-before dates between June and July 2009.