Around 500 pilot whales were found stranded in Australia’s island state of Tasmania on Wednesday.

Authorities had already been working to rescue survivors among an estimated 270 whales found Monday on a beach and two sand bars near the remote west coast town of Strahan on the island state of Tasmania.

However, rescuers managed to move 30 whales from the sandbars to open ocean.

Another 200 stranded whales were spotted from the air on Wednesday less than 10 kilometers (6 miles) to the south, Tasmania Parks and Wildlife Service Manager Nic Deka said.

“From the air, they didn’t look to be in a condition that would warrant rescue,” Deka said. “Most of them appeared to be dead.”

Further assessment of their condition would be made by boat and crews would be sent if the whales could be saved, he said.

About 30 whales in the original stranding were moved from the sandbars to open ocean but several got stranded again, Deka said.

About a third of the first group had died by Monday evening, and an update on the death toll and condition of survivors was expected later Wednesday.

Tasmania is the only part of Australia prone to mass strandings, although they occasionally occur on the Australian mainland.

Australia's largest mass stranding had been 320 pilot whales near the Western Australia state town of Dunsborough in 1996.

The latest stranding is the first involving more than 50 whales in Tasmania since 2009.

“In Tasmania, this is the biggest (mass stranding) we’ve recorded,” Marine Conservation Program wildlife biologist Kris Carlyon said.

Rescue crews remained optimistic about freeing more whales, Carlyon said.

With cool weather helping, "we’ve got a very good chance of getting more off that sandbar,” he added.

Why the whales ran aground is a mystery. The pod may have been drawn into the coast to feed or by the misadventure of one or two whales, which had led to the rest of the pod following, Carlyon said.

“It’s really likely this was the one stranding event of a big group. This would have been one big group offshore,” Carlyon said.

Marine scientist Vanessa Pirotta said there were a number of potential reasons that whales might become beached, including navigational errors.

“They do have a very strong social system, these animals are closely bonded and that’s why we have seen so many in this case unfortunately in this situation,” Pirotta told Australian Broadcasting Corp.

And rescuing them doesn't always work "because they are wanting to return back to the pod, they might hear the acoustics for the vocalizations of the sounds that the others are making, or they’re just disoriented and in this case extremely stressed, and just probably so fatigued that they in some cases don’t know where they are, " she added.

In neighboring New Zealand, more than 600 pilot whales washed up on the South Island at Farewell Spit in 2017.

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