At least 59 hospitalizations and 10 deaths have been linked to a listeria strain traced back to Boar's Head products distributed from a now-shuttered plant the company ran in Virginia.
That Boar's Head plant in Virginia had been written up dozens of times by inspectors over violations, CBS News first reported in August, based on records obtained through a Freedom of Information Act request.
Violations flagged at the plant by agriculture officials included mold and insects found throughout the site.
FSIS disclosed the existence of the probe in a letter on Thursday, when it denied a CBS News request for records on Boar's Head's other plants in Michigan, Arkansas and Indiana.
"Given the ongoing investigation related to this matter, FSIS is withholding 93 pages in full," they wrote.
An FSIS spokesperson said they were limited in the details they could share about an active investigation.
A Boar's Head spokesperson declined to comment, saying the company does not comment on legal matters. »