A large number of whales have stranded at the Chatham Islands.
DoC said it was notified last evening of the stranding of 80 to 90. Those whales were also euthanised.
About 30 to 40 whales had refloated themselves and returned to sea by the time DOC staff arrived late Thursday. "All were dead but one".
The remote and sparsely populated Chatham Islands are about 800km (500 miles) off the east coast of New Zealand's South Island. In that incident, too, government officials made the "heart-breaking" decision to euthanize the survivors to end their suffering.
"You're talking about strandings across the entire breadth of New Zealand in a very short period of time, which naturally does cause everyone to reflect on whether those might have something to do with one another", Dave Lundquist, a technical adviser on marine species, said in a video released by the Department of Conservation. "This is always an bad decision to have to make", he said.
DOC notified the local Moriori iwi and Ngāti Mutunga iwi and is working with locals to bury the whales where they stranded.
Leppens said the whales were half buried in sand and not in good health, indicating they had been there for perhaps a day before they were found.
Skin and blubber samples are being taken from the latest whales to have stranded and will be sent to Massey University scientists in an attempt to understand more about this species.
A DOC statement said marine mammal strandings were relatively common on New Zealand shores.
"Large numbers of pilot whales have been stranding for as long as we know", Russell Leaper, a whale researcher at the International Fund for Animal Welfare, told ABC News.
Fifty-one pilot whales have died after becoming stranded on a beach on the Chatham Islands off New Zealand.
The reason why whales and dolphins strand is not fully known but factors can include sickness, navigational error, geographical features, a rapidly falling tide, being chased by a predator, or extreme weather.
New Zealand's summer, the peak time for whales to beach, begins today and Stockin said more strandings were likely.
On Sunday, 10 pygmy killer whales were found stranded at Ninety Mile Beach on the North Island.