The difficult decision has been made to euthanise 20 pilot whales that have stranded again in New Zealand, but 80 refloated whales remain offshore.
Eighty of the 100 whales refloated at Farewell Spit on Saturday morning have joined the second pod of 200 whales, the Department of Conservation says.
They are offshore 6km further up the spit and will be monitored by boats.
The events are the latest update in a big rescue effort after 416 whales stranded overnight on Thursday.
About 75 per cent were dead on discovery but since then hundreds of volunteers have worked to refloat whales at high tides.
At Saturday morning's high tide boats and a human chain of rescuers worked to keep the whales at sea and keep the second pod away from the beach.
The decision to euthanise those who didn't make it was to relieve suffering.
"We are not able to successfully refloat stranded whales in every case. Even when some whales are saved, others inevitably die from injuries and the stress of being stranded, particularly the more they re-strand, as commonly occurs, and the longer it goes on," DOC says.
Massey University pathologists are carrying out necropsies on the dead whales to try to determine the cause of death.
Local iwi representatives Mairangi Reiher and Shane Graham have provided a karakia, or prayer, over the dead whales.
Mass beachings are not uncommon at Farewell Spit, where it is believed the gently shifting sandy beaches may not be picked up by the whales' echolocation.
This week's event is the third-largest recorded in New Zealand since data started being collected in the 1800s.
About 1000 whales beached themselves on the Chatham Islands in 1918 and 450 in Auckland in 1985.
The current incident comes almost exactly two years after nearly 200 pilot whales were beached at Farewell Spit.
