A humpback whale and 27 pilot whales are dead after the pod mysteriously stranded themselves on a remote Victorian beach.
Four pilot whales clung to life overnight before experts were flown in by helicopter on Wednesday to assess the mammals at Croajingolong National Park in East Gippsland.
But two have since died naturally and two were euthanised.
"We have no idea. It is a great mystery," environment department spokeswoman Gail Wright said, of the mass stranding.
"They are scattered along the beach over a long distance."
A team of experts will do skin scraps and look for bumps or lumps on the whales to see if there is a pattern, she added.
Incident controller Michael Turner suggested to AAP the pod may have "lost their bearings, or one got sick and beached itself and the others went to help" as an explanation.
It is understood the humpback whale died in a separate incident but washed up on the same shore.
The whale carcasses will not be removed by authorities.
"They will be left on the beach as it was a natural event," Ms Wright said, noting it was per protocol.
A member of the public first reported the beaching to the environment department on Tuesday.
More than 140 pilot whales died in New Zealand after stranding themselves on a beach in the country's far south on Saturday night.
It comes as authorities plan to dig up another humpback whale carcass this week after it was buried at Collendina, near Ocean Grove, since it washed ashore on November 15.
The carcass will be removed after concerns were raised by locals it would draw sharks to the area.
