The Boar's Head recalls between May and November last year have a culprit: poor sanitation.

An investigation into the multi-state Listeria outbreak by the U.S. Department of Agriculture’s Food Safety and Inspection Service identified poor sanitation practices at a Virginia facility. Boar's Head has since closed the location.

Meat and fat residue from the previous day’s products were found on production and packaging equipment; dripping condensation on products and poor building maintenance were also observed.

Facilities in Arkansas, Indiana, and Michigan were included in the investigation. Sixty-one people from 21 states became ill; 60 were hospitalized, and 10 people died.

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Agency inspectors also searched other Boar's Head facilities. The USDA said that deficiencies were corrected and monitored in both the short- and long-term at other facilities.

"This is a dark moment in our company’s history, but we intend to use this as an opportunity to enhance food safety programs not just for our company, but for the entire industry," Boar's Head said at the time.

Listeria bacteria are capable of contaminating many foods, according to the CDC. People who eat the foods can become infected by the germs and fall ill. Infection is rare, but can be serious.