Animal feed thefts in Russia may be responsible for a recent spread in African swine fever on industrial farms, according to food safety watchdog Rosselkhoznadzor.

Hog feed was stolen from industrial farms in two different Russian regions, and the bags used to carry the feed out may have come from private farms and helped spread the virus. Farm owners and veterinary officials should “pay extreme attention” to guards that work on farms, said Nikolai Vlasov, deputy head of Rosselkhoznadzor.

Roughly 76,000 pigs out of 800,000 in the Krasnodar region of southern Russia are infected with African swine fever and will be killed, said the region’s government. Governor Alexander Tkachev has declared a state of emergency in the area because of the virus.