The FDA says 12-environmental samples taken from inside the Roos Foods facility tested positive for listeria.
11 of those swabs were the same strain of the listeria outbreak that killed one person and made seven others sick.
Investigators found unsanitary conditions inside the Kenton plant, including a badly leaking roof where water was dripping onto cheese processing equipment.
Other violations found include standing water on the floor near cheese vats, a rusty metal roof and ceiling supports, and food residue found on the equipment after cleaning.
Roos has recalled many of its products, including some from its Amigo, Anita, Mexicana and Santa Rosa De Lima brands.