An outbreak of botulism tied to ByHeart baby formula has made at least 15 infants sick in 12 states, a California health official said Monday.

Nine cases of infant botulism type A have been confirmed, with results on six others pending, said Dr. Erica Pan, health officer for the California Department of Public Health. That's an increase from 13 cases in 10 states reported on Saturday .

Federal and state officials are investigating the outbreak, which began in mid-August. No deaths have been reported.

ByHeart, a maker of organic baby formula based in New York, recalled two lots of its Whole Nutrition Infant Formula over the weekend.

The recall affects products labeled with the following batch codes and use-by dates, which can be found on the bottom of the can:

Batch Code: 251261P2,

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