Flinders University little penguin monitoring cameras have revealed there were at least two foxes on Granite Island in late June, when five of the birds were killed.
In video footage from the morning of June 24, when the first penguin carcass was found, a pair of foxes are seen sniffing in burrows on Granite Island's north shore.
Flinders University penguin ecologist Diane Colombelli-Negrel said five deceased penguins have been found with injuries consistent with fox attacks.
She said there could be others which have not yet been found, including one taken by a fox in front of local penguin monitor Stephen Hedges.
Since the attacks at the end of June, the island and the remaining few penguins have been closely monitored by Dr Colombelli-Negrel and the team of local guides.
A Department of Environment and Water spokesperson said while the department was still waiting for autopsy results, "injuries appear to be consistent with fox attack".
The spokesperson said they were "confident one of the foxes is likely dead", as one of the baits laid by Nationals Parks and Wildlife Service SA had been taken.
"Other baits remain in place, however the second fox has not been seen on the island for more than a week," they said.
"At the moment, all we can do is keep an eye on it and work with DEW to catch the fox, if it's still alive," Dr Colombelli-Negrel said.
Owners are urged to keep dogs away from the island as baits laid are highly toxic.
See videos of the penguins and foxes at www.victorharbortimes.com.au