The organization said its Humane Law Enforcement Unit received a call on Monday from a landlord after neighbors started complaining about a bad smell coming from an apartment.
Rescuers said they discovered nearly 40 terrified cats living in filth and garbage.
They said the animals are all dehydrated and most are sick with severe upper respiratory and ear infections.
Rescuers set up food and water stations but think it might take days to rescue all of the animals. They have vowed not to stop until every single animal is rescued.
"It's not livable conditions within a minute of being inside," said SPCA Westchester's Lisa Bonanno. "You can't really breathe. It's really unhealthy."
Authorities said they're working to relocate the resident who has been cooperative with animal rescue workers. No charges will be filed against the resident living in the apartment.
Rescue workers estimate it will take weeks to assess, treat, spay and neuter the cats before they are healthy enough to be put up for adoption. The relocated cats are being treated at SPCA Westchester in Briarcliff.
RELATED | More than 100 exotic animals confiscated from North Bellmore basement and backyard
More than 100 exotic animals rescued from Bellmore home
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