Originally, the family pet suffered only a concussion and some cutsin the attack, but continued to experience pain overnight Wednesday and Thursday morning.
Owner Felicity Simmons said 16-year-old Lilly "hadn't been herself" since the incident and still appeared to be in considerable pain.
"Lilly is not too great today. She's about to go back to the vet for some IV fluids and pain relief," she said.
Sixteen-year-old cat Lilly suffered a concussion and some cuts in the attack. Photo / Supplied
Simmons said there was no update on the investigation and she was still awaiting some CCTV footage from a storage facility near her property to assist the Police.
The SPCA confirmed this afternoon that the investigation was now sitting with Police due to the possibility of the offenders being minors.
Police said that they were still investigating the incident, and that "information provided is being assessed".