Fifty-one pilot whales became stranded and died on a beach in the Chatham Islands in New Zealand.
It is the second mass stranding in a week after 145 pilot whales were found dead on the country's far south Stewart Island on Monday.
Officials were notified of around 80 to 90 whales that became stranded on Thursday evening.
When staff arrived the following morning, around 30 to 40 of the whales had managed to return to sea.
But all the remaining whales were dead, bar one that had to be euthanised.
The Department of Conversation Chatham Islands operations manager Dave Carlton said: “There was no likelihood of being able to successfully save the remaining whale. Sadly, the decision was made to euthanise. It was the most humane thing to do."
"This is always an awful decision to have to make.”
As is common practice in New Zealand, officials worked with local Maori communities to bury the whales at the site.
Skin and blubber samples were taken from the whales for analysis.
Marine mammal strandings are a relatively common occurrence on New Zealand shores.
Ten pygmy killer whales also became stranded on 90-mile beach in Northland on Sunday.
It is not fully known why strandings happen but the department said factors can include sickness, navigational error, geographical features, rapidly falling tide, being chased by a predator or extreme weather.
