The U.S. Food and Drug Administration and the Centers for Disease Control and Prevention said on Monday the agencies were investigating a multi-state outbreak of listeria infections linked to frozen supplemental shakes manufactured by Prairie Farms Dairy Inc.

According to a CDC food safety alert, an outbreak of Listeria infections has affected 38 people across 21 states. Of those infected, 37 have been hospitalized, and 12 have died.

Twelve deaths have been reported as part of an outbreak of Listeria monocytogenes infections linked to frozen supplemental shakes, the US Food and Drug Administration said Monday. At least 38 people in 21 states had been infected,