ROME (AP) — Police in Italy have shut down a mozzarella factory and arrested 13 people after finding that prized local buffalo milk was being cut with cheaper imported cow milk.

Authorities also found that the cheese, produced near the southern town of Caserta, contained as much as 20 times permissible levels of bacteria, said Carabinieri Police Maj. Alfonso Pannone.

Police on Monday also shut down seven stores selling the cheese in the Campania region which includes Naples.

Milky white buffalo mozzarella is prized by Italians and tourists. It carries a special label supposed to guarantee quality and protect its reputation.

Among those arrested were two public health service veterinarians who allegedly tipped the factory to upcoming inspections. The probe began after a worker lost some of his fingers because of safety flaws.