More than 20 pilot whales have died stranded in mysterious circumstances on the south-western coast of Iceland, emergency services said Saturday, only two weeks after a similarly unexplained mass stranding had already killed dozens of the long-finned cetaceans.
The dead whales, part of a group of 50 stranded whales, were discovered late Friday near Gardur, some 50 kilometres (31 miles) from the capital Reykjavik.
According to Icelandic media, locals began rescue efforts to save the whales even before emergency teams arrived.
"Around 90 volunteers worked all night to keep the animals wet," David Mar Bjarnason, a spokesman for the Icelandic research and rescue association, told AFP.
"We had to wait for high tide to get them back into the sea," Bjarnason said.
Pilot whales are relatively plentiful, with their stock in the Atlantic estimated at between 500,000 and 800,000 animals.
Last month 60 dead stranded whales were spotted on a remote beach in the west of the North Atlantic island nation.
Pilot whales, which belong to the dolphin family and feed primarily on squid, can sometimes get stuck if they follow their prey into shallow coastal waters.
But scientists are mystified as to why such large numbers should get stranded at the same time.
Some theories mention magnetic field interference, while others say that a pod of pilot whales will always follow a single leader even if that dominant whale leads them into mortal danger.
Just two weeks ago dozens of dead beached whales were spotted by sightseers during a helicopter flight over western Iceland.
The dead pilot whales were photographed during the trip over a beach at Longufjorur.
It's unclear how the mammals became beached.
The region where they were spotted is secluded, inaccessible by car and has very few visitors.
Police in the nearby town of Stykkisholmur has been made aware of the discovery, local media say. The images were taken by helicopter pilot David Schwarzhans.
He told the BBC: "We were flying northbound over the beach and then we saw them.
We were circling over it not sure if it was whales, seals or dolphins.
We landed and counted about 60 but there must have been more because there were fins sticking out of the sand.
"It was tragic and when we stood downwind it was smelly.
It wasn't something nice to see and quite shocking since there were so many".
Edda Elisabet Magnusdottir, a marine biologist and whale expert, told Iceland Monitor that when such mammals enter shallow waters "most of them have a tendency to become disorientated".
She added that pilot whales usually swim in tight groups, which is why so many of them become stranded at once.
In November 2018, about 145 pilot whales were found beached on an island in New Zealand.
Half of the whales had died by the time they were discovered, while the remaining were put down as it would have been too difficult to save them.