The 51 New Zealand fur seal pups found on a South Australian beach may have abandoned.
Vets remain baffled by the unprecedented deaths despite post-mortem examinations on Tuesday on three of the pup bodies found dead on a beach on the Eyre Peninsula on Sunday.
Adelaide University veterinary pathology lecturer Lucy Woolford said the tests were so far inconclusive but further samples would be examined.
"They weren't emaciated, there were no obvious signs of trauma," Dr Woolford told AAP.
"We are thinking it's either an infectious cause or some kind of incident that has caused an abandonment-like situation or mismothering."