In the wee hours of Monday morning, a car pulled up to the Marin Humane Society in Novato, leaving behind three boxes.

Inside were 24 so-called tuxedo cats, named for their distinctive black and white markings. It was the fourth such occurrence in the last 18 months, said spokeswoman Lisa Bloch, leaving the shelter to care for more than 100 felines.

All the cats, which range in age from kitten to full-grown, appeared to be in good health, with no fleas or diseases. The humane society is simply overrun with animals and is having trouble housing the abandoned felines.

“Every cage is full and our staff is overloaded trying to care for them all,” Bloch said. “It’s putting a big strain on us.”

The person who’s responsible for leaving the cats has been caught on surveillance tape — and Bloch said it appears to be the same person every time. The shelter isn’t looking to punish the person, however, but instead wants to offer information about getting pets fixed.

“We don’t know if this person is some kind of hoarder or if they are just a well-intentioned owner,” Bloch said. “But we would really like them to know about getting their cats spayed or neutered. We’re concerned that it will keep happening and we want to break that cycle.”

The shelter is currently housing about 180 cats, just about its limit. To help find all of the felines loving homes, officials will be waiving cat and kitten adoption fees through the end of the month.