Fifteen pilot whales have died after a mass stranding at Port Levy on Banks Peninsula.
Department of Conservation personnel and local people managed on Sunday to return half a dozen to the water and a further 50 followed.
Project Jonah chief executive Kimberly Muncaster says mass strandings in this part of the country are very unusual.
Ms Muncaster says stranding hotspots include the far North and Golden Bay, but she can't recall a mass stranding on Banks Peninsula for the last 100 years.
She says the whales may have become disorientated in the shallow sandy harbour while searching for food.
Scientists will take samples on Monday to try and establish what caused the stranding, and the dead whales will be buried after consultation with local iwi.
