Procopio said the pit bulls appeared to have been the target of the burglars because other breeds of dogs were left behind during each burglary.
"I think they feel they can be sold as purebreds even though they are mixes. And some people use pit bulls for fighting," she said.
The pets are at risk because puppies and pregnant dogs are susceptible to viruses and need proper nutrition, said Procopio.
The pups are Dante, a 9-week-old male; China, a 7-month-old female; Jade, a 3-month-old female; Eve, a 9-week-old female; Bruno, a 6-week-old male, and Odie, a 9-week-old male.
Although Kali had bitten her previous owner, Procopio said she was provoked and does not have a volatile temper.
If sold as a purebred, a pit bull can bring $100 to $150, she said.
If they aren't sold, the animals likely will be used for fighting and the weaker dogs will be used for training, she said.
Pit bulls are popular because of their strong, compact bodies and their ability to be extremely aggressive if encouraged, she said.
Pit bulls have above-average intelligence and strength but aren't vicious unless trained to be, said Procopio.
Factors such as neglect, abuse, indiscriminate breeding and poor nutrition in its formative years can make a dog of any breed inclined to be violent, she said.
The pit bull has become the dog of choice for suspected drug dealers and other criminals in Hagerstown, said City Police Chief Arthur Smith.
The dogs are chosen by criminals as status symbols and for protection, he said. City residents have complained about the dogs.
Smith's experience with the breed has shown that "they don't just bite - they bite and hold on to do damage."
The city is researching different pit bull ordinances to see if any are appropriate for Hagerstown, said Smith.
A Washington County Sheriff's deputy is investigating the thefts. Anyone with information may call 301-791-3020.
The humane society is offering a cash reward for information about the pit bulls. If those responsible return the animals there will be no questions asked, said Procopio.