Video: 51 whales die after mass stranding in Western Australia

More than 50 pilot whales have died hours after stranding themselves on a beach in Western Australia, with authorities saying on Wednesday that they are scrambling to save dozens more.

A pod of almost 100 long-finned pilot whales was spotted off Cheynes Beach near Albany, about 400km southeast of Perth on Tuesday evening.

Experts from the state's Parks and Wildlife Service were joined by volunteers, who worked through the night, braving cold temperatures to monitor the whales.

The service confirmed on Wednesday morning that 51 of the animals had died.

The organisation said it is now working with volunteers to try and save the remaining 46 whales, with plans to guide them to deeper water during the course of the day.

Footage from the scene showed volunteers, many of them wearing wetsuits, working busily to help the thrashing mammals on the shores of the beach.

A spokesperson for the Parks and Wildlife Service said it had been "overwhelmed with hundreds of offers of help" but that it had enough volunteers and the public should "stay away" from the beach "for safety reasons".

"The priority focus of the Incident Management Team is to ensure the safety of staff and volunteers and the welfare of the whales," they said.

"The response zone has a range of hazards, including large, distressed and potentially sick whales, sharks, waves, heavy machinery and vessels."

Mass strandings of pilot whales are not uncommon in Australia and New Zealand.

Last October, around 500 pilot whales died when they beached on the remote Chatham Islands in New Zealand.

Scientists do not fully understand why mass strandings occur, but pilot whales — which can grow to more than 6m long — are highly sociable, so they may follow pod-mates who stray into danger.