Sixteen dead cats have been drowned and dumped in bushland at Silverdale.
St Marys Local Area Command police officers were called by a local rescue group who discovered the bodies in varying stages of decompisition.
The cats were found in bushland at the rear of industrial complex in Econo Place, Silverdale on Thursday, August 10.
Post mortem examinations were conducted on some of the bodies, which indicated those cats had been drowned.
Police have been told the cats were living in bushland and none appear to have been micro-chipped.
Police are working with the RSPCA, the rescue group and local businesses in an effort to identify who is responsible for the deaths.
Police are urging anyone with information in relation to this incident to call Crime Stoppers on 1800 333 000 or use the Crime Stoppers online reporting page: nsw.crimestoppers.com.au