The Food Safety Authority says a range of widely used brands of plain flour may be a possible source of a recent outbreak of salmonella.
Some 36 cases of the strain Salmonella Typhimurium Phage type 42 have been reported from Auckland to Dunedin - 16 of those in Christchurch.
Brands of flour likely to affected are: Champion, Edmonds, Homelife and Pam's plain flour with best-used-before dates between June - July 2009.
The companies have voluntarily withdrawn the products.
Carol Barnao from the FSA told Morning Report that extensive testing is being done on the flour products.
She said the evidence is not conclusive, but indicates the people who got sick are more likely to have eaten uncooked flour - for example in home-made play dough, raw cake and batter mixes.
She said there's no concern about the cooked product, but home bakers should avoid consuming what's left in their mixing bowls.