The Department of Conservation is carrying out tests to establish the reason for the recent stranding and subsequent death of two whales on Ripiro Beach near Dargaville.
Thought to be a pygmy sperm whale, locals discovered an adult female stranded about six kilometres north of Glinks Gully around 1.30pm on Sunday.
DoC was notified and the Te Kopuru Fire Brigade was also called for assistance.
Michael Ross was one of about 10 people, including two tourists from Slovakia, who spent over an hour refloating the two-and-a-half metre whale which swam off towards Glinks Gully.
A juvenile stranded at Mahuta Gap further down the beach was also refloated by another group of volunteers and swam out to sea.
Mr Ross said concerns have arisen over reports that witnesses had seen a second baby whale being dragged down the beach by members of the public and heard it had later been shot.
DoC spokesman Darren Jones yesterday confirmed a juvenile whale had been euthanised without the department's knowledge.
He said DoC had recovered the body and an autopsy revealed the male baby was seriously ill and would have suffered a painful and lingering death without being euthanised.
However, he reminded members of the public finding sick or injured wildlife to contact DoC or Ministry of Fisheries staff and not take matters into their own hands.
DoC is responsible for the protection, conservation and management of marine mammals within New Zealand waters, regardless of whether the mammals are dead, beach-cast or stranded.
The female rescued at Glinks Gully was found later in the day stranded about one kilometre north of the Baylys Beach settlement. Seriously sick and not expected to live, she was euthanised.
Kauri Coast area manager Meirene Hardy-Birch said: "Euthanasia is a difficult decision made for the welfare of the animal."
Tests and photos confirmed it was the same adult whale which had been refloated at Glinks Gully.
It is hoped further tests will reveal why the whales stranded.
If you come across a stranded whale, call 0800 362 468 or 0800 DOC HOT.