General Mills Inc. issued a voluntary recall Tuesday of about 10 million pounds of flour, saying it was working with health officials to investigate an outbreak of E. coli that has sickened 38 people in 20 U.S. states. The bacteria strain behind the outbreak has not been found in any of General Mills' Gold Medal, Wondra and Signature Kitchens flour or their manufacturing plant, the company said. Nor have consumers have not contacted it directly to report any illnesses. "Out of an abundance of caution, a voluntary recall is being made," the company said. U.S. and state health authorities are probing an outbreak of E. coli O121 from Dec. 21 to May 3, General Mills said.