General Mills Inc. is voluntarily recalling an estimated 10 million pounds (4.5 million kilograms) of flour over E. coli concerns after customers who used the baking staple reported getting sick during the last five months.

The Centers for Disease Control and Prevention found that approximately half of the 38 people who were infected with a specific strain of E. coli had reported making something with flour before getting sick, General Mills said in a statement Tuesday. The company added that “some of the ill consumers may have also consumed raw dough or batter.” The outbreak, which began in December, has spanned 20 states.

“We felt it was important to not only recall the product and replace it for consumers if there was any doubt, but also to take this opportunity to remind our consumers how to safely handle flour,” said Liz Nordlie, president of General Mills’ baking division.

General Mills hasn’t actually found the E. coli strain in any of its flour products or in the flour manufacturing plant. The Minneapolis-based company hasn’t been contacted directly by any consumers reporting illnesses.

The recall covers six types of flour sold under the Gold Medal, Wondra and Signature Kitchen brands.