General Mills on Tuesday issued a voluntary recall of about 10 million pounds of flour, saying it was working with health officials to investigate an outbreak of E. coli that had sickened 38 people in 20 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 in a statement. Consumers have not contacted it directly to report any illnesses, Minneapolis-based company added.

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"Out of an abundance of caution, a voluntary recall is being made," General Mills said in a statement.

U.S. and state health authorities are probing an outbreak of E. coli O121 from Dec. 21 to May 3, General Mills said in a statement. The potentially deadly strain can cause bloody diarrhea and dehydration, mostly among the elderly, very young children and people with weak immune systems.

The Centers for Disease Control found that about half of the 38 sickened people reported cooking with flour before becoming ill, General Mills said. About half of this group reported using a General Mills brand, a company spokesman said in a phone interview.

Additional recall information can be found at  www.generalmills.com/flour.