At least a third of 270 whales stranded off the coast of Australia's Tasmania have died and more are feared to be dying, rescuers say.
The mass stranding on the west coast of the island was discovered on Monday, reports BBC.
Marine biologists are scrambling to save the remaining pilot whales in a tricky operation likely to take days.
It's unknown what drew the whales to the shore. Whale beachings are common in the region, but one of this size has not been seen since 2009.
Scientists from the Tasmanian Maritime Conservation Program said the whales were found in three groups across Macquarie Heads - a remote tip of the island with limited vessel and road access.
Rescuers arrived at the scene late on Monday, discovering hundreds more animals in peril than had been first spotted from the air.
A full assessment was yet to be achieved on Tuesday, as "most of the animals are relatively inaccessible", wildlife biologist Dr Kris Carlyon told reporters.
However attempts to save the first ones began on Tuesday.
"We will take the animals with the best chance to start with," Dr Carlyon said, adding that some of the animals may simply be too big or in an unsuitable location.
Pilot whales can grow up to to seven metres long and weigh up to three tonnes.
About 200 of the mammals had washed up on a sandbar near a boat ramp, while 30 others were found several hundred metres away. Another 30 were found further inland along Ocean Beach.
Whales travel in pods and make seasonal migrations up and down the coast of Australia and New Zealand.
Researchers say they follow a leader and their strong social bonds can lead to whole groups beaching themselves.
In New Zealand in 2018, more than 200 pilot whales died over the course of a week following separate strandings off the nation's east coast.