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The Department of Conservation was first alerted to the mass stranding at the base of Farewell Spit in Golden Bay by a tour operator at 9.30am today.
A spokesperson said nine of the original 49 whales had died.
Around 65 people have gathered at the site to assist.
DOC aimed to refloat the whales once the water was deep enough and rangers was on site to assist them.
DOC ranger Amanda Harvey told RNZ's Checkpoint programme tonight that the incoming tide had reached most of the pod, although there were concerns that one large whale was not responding as much as they would like.
Project Jonah was taking out a pontoon to try to encourage it to head to sea.
Harvey said it looked as if the whales had never stranded before because they did not bear any marks or abrasions and they were in very good condition.
Conditions were extremely good for a refloat, she said.
Some volunteers have now been relieved by others who will handle "the wet phase".
"The idea is to group them [the whales] as much as possible together."
Harvey said it was often a female that took the lead.
"The idea is to get them together and let them decide and take it from there."
Boats and spotters will follow them until it is dark.
Some volunteers would stay on the beach overnight because it was possible they could strand again in the early morning, Harvey said.
Farewell Spit had been the frequent site for whale strandings and scientists were still trying to work out why.
The last mass pilot whale stranding on Farewell Spit was in February 2017 when an estimated 600-700 whales were beached.
About 250 died while the rest were refloated.