A nationwide salmonella outbreak may have been caused by bacteria contained in flour, the New Zealand Food Safety Authority (NZFSA) says.
Plain flour manufactured under the Champion, Edmonds, Homelife and Pam's brands with best-before dates between June and July 2009 may be affected, said authority spokesman Geoff Allen.
The manufacturer launched a voluntary withdrawal after being contacted by the NZFSA.
The affected batches of flour could be used safely if properly cooked.
Investigations were continuing into the source of the bacteria, which was found in the home of one of the affected people, Mr Allen said. A sample from the home of another person was provisionally confirmed as positive.
People with the infection, particularly children, were likely to have eaten uncooked flour in home-made playdough or raw cake batter, said Ministry of Health spokesman Dr Greg Simmons.
"It is possible for low levels of bacteria to be on wheat or other points of the flour milling process, and studies indicate that about one percent of flour on average contains salmonella," Dr Simmons said.
Flour was intended to be eaten cooked, and was not expected to be a sterile product.
"If people have used these brands in their baking - for biscuits, cakes, breads or other Christmas treats - they can be reassured that the cooking will have killed the bacteria and that these home baked foods are safe to eat," he said.
The NZFSA recommended people wash hands before and after handling food and ingredients, thoroughly cook foods, and not eat raw batter or mixes containing uncooked baking ingredients.
