(CNN) As many as 145 whales have died after being found stranded on a remote beach in New Zealand, conservation officials said Monday.

Two pods of pilot whales were discovered just over a mile apart on Mason Bay, Stewart Island, a sparsely populated island in the country's south.

Authorities were first alerted to the mass stranding by a hiker Saturday evening. Half of the whales were already dead. The remaining animals were later euthanized, according to New Zealand's Department of Conservation (DOC).

A Stewart Island operations manager for the DOC, Ren Leppens, said that the remote location and condition of the surviving whales made it impossible to save them. He described the decision as "heart-breaking."

"Sadly, the likelihood of being able to successfully re-float the remaining whales was extremely low," Leppens said in a statement . "The remote location, lack of nearby personnel and the whales' deteriorating condition meant the most humane thing to do was to euthanize."

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