Officials are executing a search warrant at the PetSmart in Bellevue.
According to Metro Animal Control, the investigation involves less than 10 small rodents.
The Metro Health Department and Metro Animal Control will be asking for veterinary records for the animals.
The animals that are injured will be confiscated so they can receive the care that they need.
Officials said they received information and photos that the animals were not receiving proper veterinary care.
PETA claims they provided law enforcement with video and photo evidence of the neglect documented by someone who worked at the store.
According to the organization, multiple managers repeatedly refused to provide veterinary care to sick, injured and dying animals so they could keep costs down.
One of the animals that died was a guinea pig whose abscessed knee joint spread an infection to his heart and brain, according to PETA.
PETA's investigation also included stores in Florida and Arizona.