Reading police said 61-year-old Christine Kramer was in critical condition Monday and being treated for smoke inhalation.
Fire officials said about 17 cats died in the fire, as well as a dog and two birds. Six other cats were treated at the scene with animal oxygen masks and are being cared for at the Animal Rescue League.
Investigators said the blaze broke out shortly before 2 a.m. Monday and was the result of unattended cooking.
Acting Fire Chief Gary Mogel said damage was estimated at $25,000 to $30,000. He said the house did not seem to have any working smoke detectors.