UPPER DARBY — A pizzeria owner with mice problems he blamed on competitors tried to sabotage two rival shops by dumping mice in them Monday, authorities in suburban Philadelphia said.

Upper Darby police said a man walked into Verona Pizza on Monday afternoon and asked to use the bathroom. After he left, the owner said he found footprints on the toilet and noticed that the drop ceiling had been disturbed, and he found a bag tucked up above.

The owner turned the bag over to two police officers who happened to be eating lunch there, and they found three white mice inside, police Superintendent Michael Chitwood said.

Police say the man then walked across the street to Uncle Nick’s Pizza and dumped another bag into a trash can inside the establishment. Police found five live mice and one dead one inside.

“We have never had anything like this where mice have been used as an instrument of crime,” Chitwood said. “This is food terrorism by mice.”

Nikolas Galiatsatos, 47, owner of Nina’s Bella Pizzeria a few blocks away, faces charges of disorderly conduct, harassment and animal cruelty, police said.