It turns out mom was right about the dangers of raw cookie, but possibly for the wrong reason.

Many people assume raw egg in cookie dough is what makes people sick, but raw flour can spread foodborne illness to humans through contaminated grain, according to new findings published Tuesday by the Centers for Disease Control (CDC) and U.S. Food and Drug Administration following their investigation into an E. coli outbreak linked to flour made by General Mills.

So far 38 people, including three in the Twin Cities, across 20 states have been sickened by a less common strain of bacteria, Shiga toxin-producing E. coli O121, that can cause diarrhea, cramping and dehydration. Ten people have been hospitalized and no deaths have been reported.

And while many people associate food pathogens with uncooked eggs and meats, flour can carry diseases from the field to consumers' kitchens. Eating or handling raw dough was a common theme among some of the patients, and investigators warned the public on Tuesday not to eat cookie dough.

The CDC and FDA went a step further by cautioning restaurants not to give customers raw dough. This was apparently necessary as some of the recalled flours were sold to restaurants that give children "play dough" made from raw ingredients.

"Flour is derived from a grain that comes directly from the field and typically is not treated to kill bacteria," said Leslie Smoot, a senior advisor at the FDA's food safety office.

Flour that has been exposed to manure or other animal waste could become tainted prior to harvest and milling. The FDA says illness can be avoided by using a common "kill step" during food prep, such as boiling, frying, roasting, baking and even microwaving. And even though the summer heat may inspire some homemade ice cream, the CDC and FDA cautions against stirring up a batch of cookie dough flavor.

On May 31, Golden Valley-based General Mills voluntarily recalled more than 10 million pounds of flour suspected to have caused the outbreak. The three brands are Gold Medal, the nation's top-selling flour, Signature Kitchen's and Gold Medal Wondra. The recall cuts across varieties, including unbleached, all-purpose and self-rising.

The investigation traced the contamination to flour produced at a General Mills plant in Kansas City.