The U.S. FDA 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.

The Centers for Disease Control and Prevention (CDC) is urging people to check their supplement shakes after a Listeria outbreak.

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,