Authorities were called to a boarding house on the 1500 Block of N. 12th Street on Friday.
The owner of the cats, a male in his 30s, was being evicted by the landlord who suspected him of keeping a large number of cats in his small rented room.
In addition, the landlord reported an increasingly strong odor emanating from the room. When the landlord let the officers in, they discovered not only 12 cats in poor physical shape living in unsanitary conditions, but also an additional 17 deceased cats.
Many of the dead animals were being kept in the freezer portion of a refrigerator in the room and varying locations throughout the room, the SPCA said.
"This is definitely one of the more bizarre cases we've seen," George Bengal, Director of Humane Law Enforcement for the Pennsylvania SPCA said in a statement. "The small room and conditions these cats were living in was unbelievable."
The homeowner, who lives with his elderly frail mother, tells authorities they began renting the room to an Asian man in his 30's a few years ago.
Officials say the owners were not aware that the man had gathered so many cats.
Neighbors reacted to the disturbing findings of the SPCA in the small apartment.
"I wouldn't know the mindset of the person. They have to be sick to do something like that, because that's really nasty, that's disgusting," said Katherine Davis.
"The air quality was really hard to breathe," said Derrick Schlitter of the SPCA. "You really couldn't go in without a mask."
"It's pretty bizarre in the fact that there was so many of them, occasionally you'll find one or two deceased animals, but there were a high number of them in different stages of decomposition and there were a couple skeletons," described Schlitter.The live cats were brought back to the Pennsylvania SPCA headquarters where they are being evaluated and treated by the veterinary staff.
The cats will be held in protective custody and are not currently available for adoption.
Humane Law Officers are in the process of locating the suspect. Animal cruelty charges are pending.