Miller said two carcasses were sent for testing to the Maryland Department of Agriculture Animal Health Laboratory in Frederick, Md., but the results of the autopsies were inconclusive.
The shelter is asking residents who find stray cats to keep the cats until shelter workers are able to determine "the exact problem within the shelter cat population and take the necessary steps to control and/or eliminate it," according to the release.
"I'm trying to slow down my intake," Miller said.
Miller said he's not sure if the cause of the cats' deaths is due to feline distemper, which he said "is highly suspicious," but he said the disease is a common culprit at shelters throughout the country, causing some to lose "hundreds of cats."
"It's very contagious," he said.
According to the American Veterinary Medical Association's Web site, feline distemper, also called feline panleukopenia, cat fever and cat typhoid, is a virus that kills rapidly dividing body cells. The cell loss makes the cat more susceptible to other complications and bacterial infections.
The first signs of the virus are generalized depression, loss of appetite, high fever, lethargy, vomiting, severe diarrhea, dehydration or hanging over the water dish, according to the Web site.
Miller said it's important to get cats vaccinated for diseases.
"We're looking for common denominators now," he said. "We're seeing if they can tell us anything at all."
Animals that have been attacked or exposed to rabies, animals that have bitten someone, owned animals brought in for euthanasia and stray animals that are sick or injured will continue to be accepted by the Humane Society, according to the release.
Dogs, rabbits, guinea pigs and ferrets will continue to be accepted, according to the release.
The Humane Society asks residents who find stray animals to report them to the lost and found department at 301-733-2060, ext. 209.