A humane society official went to the west end apartment over a store Friday to speak to the unidentified woman, but she slammed the door on him, the Toronto Star reported Wednesday.
Jerry Higgins said he returned four hours later with a warrant and police officers.
They removed 30 cats, many of them ill with respiratory infections, Higgins said. Two of the cats were so ill they had to be euthanized. The remainder were divided among three animal shelters and won't be put up for adoption until they recuperate and pass quarantine observation, the report said.
"Thirty cats were rescued from the same address two years ago," Higgins said.
The woman's neighbors, who described her as being in her 70s, wasn't charged two years ago and it wasn't immediately known if she would be charged in the most recent animal hoarding incident.