“The conditions that the team faced yesterday in attempts to refloat the whales proved very challenging and in fact, dangerous to our staff,” Tasmania Parks and Wildlife Service Brendon Clark said in a media briefing.
Read more: In Pics | Over 150 false killer whales stranded on Tasmania beach in first mass stranding in 50 yearsA total of 27 animals were euthanised on Thursday morning while 38 were still alive, Clark said.
The euthanasia process is expected to finish later on Thursday.
Officials have said the stranding response would be complex due to the inaccessibility of the site, ocean conditions and the challenges of getting specialist equipment to the remote area.
The animals can grow up to 20 feet (6.1 m) long and weigh up to 3,000 lbs (1,361 kg). They are found in all tropical and subtropical oceans, generally in deep offshore waters, according to the U.S. National Oceanic and Atmospheric Administration.