A baby formula recall linked to an infant botulism outbreak is expanding. Here's what to know.

"California officials confirmed that a sample from an open can of ByHeart baby formula fed to an infant who fell ill contained the type of bacteria that causes the toxin linked to the outbreak. The tests to confirm contamination involve injecting mice with the cultured bacterium and then waiting up to four days to see if they get sick, said Dr. Erica Pan, the state health officer. "These mice got sick really quickly," Pan said in an interview."

"ByHeart officials said they recalled their products "in close collaboration" with the U.S. Food and Drug Administration, despite the fact that no previously unopened product tested positive for the illness-causing bacteria. The type of bacteria that produces the toxin is widespread in the environment and could come from sources other than the formula, company officials said."

"The outbreak has sickened babies age 2 weeks to 5 months since it started. The infants were hospitalized after consuming ByHeart powdered formula, according to the U.S. Centers for Disease Control and Prevention. At least 15 babies in 12 states have been sickened in the outbreak tied to ByHeart formula, state and federal health officials said. That's an increase from 13 cases in 10 states reported Saturday. No deaths have been reported in the outbreak, which began in August."

An outbreak of infant botulism beginning in August has led to hospitalizations of infants aged 2 weeks to 5 months. At least 15 infants in 12 states consumed ByHeart powdered formula and became ill; the U.S. Food and Drug Administration is investigating 84 infant botulism cases detected since August. California officials found the outbreak-linked bacteria in an open can using a mouse bioassay, with mice becoming sick quickly. ByHeart recalled its products and advised parents and caregivers to stop use and dispose of the formula. Company statements noted no previously unopened product tested positive and that the bacteria are widespread in the environment. No deaths have been reported.

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