About 10 whales have died in a stranding of nearly 40 pilot whales at Farewell Spit in Golden Bay.
Rescuers, Department of Conservation rangers and the local community have been working to refloat the whales since being alerted on Monday.
Project Jonah's Louisa Hawkes told Morning Report some whales restranded overnight.
Seven died during the night and one was put down, after three died on Monday, she said.
Hawkes said rescuers would be attempt to refloat about 20 whales at high tide on Tuesday.
"They've split into two pods - a few have remained where the pod stranded yesterday but the majority have moved towards the sea so they'll have more ocean around them quicker than the ones have remained where they were yesterday.
"It's tricky conditions - the wind is picking up," she said.
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