''That's where the investigation is now and we can't do anything further until we get more information from the public.
"We're relying on the public to act in good faith,'' the organisation's executive officer, Sophie McSkimming, said yesterday.
There was a public outcry when the 12-week purebred huntaway male puppy was found by a teenage fisherman in the Clutha River on July 21.
The puppy had apparently been tied to a schist rock and thrown into the river near the Alexandra bridge.
''We know how horrified people were about the drowning, as we were, and there was such an outpouring of support, especially from Alexandra people.
"It would be nice to be able to do something with that support. Someone must have said something,'' Ms McSkimming said.
Information about the identity of the puppy's owner would also be useful.
Anyone with information about the incident can contact the SPCA on 0800 682-467.
