Cartons of frozen shakes sold to nursing homes and other institutions are being recalled after an outbreak of listeria linked to the products.

The supplemental shakes are labeled under the brands Lyons ReadyCare and Sysco Imperial and were sold to institutional customers, including hospitals and long-term care facilities, the U.S. Food and Drug Administration said Friday.

The Centers for Disease Control and Prevention said listeria cases linked to the products date to 2018 but investigators had been previously unable to identify the source. Some 38 people were infected with listeria, including 11 who died. The FDA's investigation is still underway.