Federal and state health officials are investigating an outbreak of E. coli O121 that has caused 38 cases of illness across 20 states, the Centers for Disease Control and Prevention said Tuesday. Ten of those individuals have been hospitalized.

Out of an abundance of caution, General Mills announced the voluntary recall of more than 10 million pounds of flour because it may be linked to the outbreak.

Approximately half of the ill individuals reported making something homemade with flour before becoming ill, and some of them reported using a General Mills brand of flour, the company said in a news release.

The illnesses occurred between December 21 and May 3, according to General Mills.

"To date E. coli O121 has not been found in any General Mills flour products or in the flour manufacturing facility, and the company has not been contacted directly by any consumer reporting confirmed illnesses related to these products," the company said, adding that some of the ill individuals also consumed raw dough or batter.

Eating raw dough or batter that is "intended for cooking" is not recommended. It also should not be given to children to play with, according to the CDC.

Symptoms of E. coli illness can include stomach cramps, diarrhea, vomiting and fever that can last five to seven days. Individuals who are very old or very young and those with compromised immune systems have an increased risk of becoming ill.

The recall includes Gold Medal flour, Wondra flour and Signature Kitchens flour. All three brands were sold at Safeway, Albertsons, Jewel, Shaws, Vons, United, Randalls and Acme retailers.

Consumers who have recalled flour should not use it. Contact General Mills with any questions.

E. coli outbreak prompts massive flour recall