Recalled supplemental shakes were distributed to hospitals and long-term care facilities nationwide, federal officials say.

A listeria outbreak linked to frozen nutritional milkshakes is to blame for 12 deaths and dozens of hospitalizations, the U.S. Food and Drug Administration confirmed Monday following an investigation that spanned years.

Listeria-tainted frozen shakes served at hospitals and long-term care facilities have sickened at least 38 people and resulted in the deaths of 12, the Food and Drug Administration said. The FDA’s investigation is ongoing.