A pod of 107 pilot whales stranded on a remote New Zealand beach have died, including 48 that were put down, the government's conservation department said.

The stranded whales were discovered by hikers on Sunday near Cavalier Creek on Stewart Island, off the southern tip of New Zealand's South Island.

Conservation department staff flew to the area and found that about half of the group were already dead and the others were dying, the agency said. The whales were well up the beach and the tide was receding, leaving little chance of keeping them alive until more rescuers could arrive.

"Euthanasia is a difficult decision, but is made purely for the welfare of the animal involved to prevent it from prolonged suffering," said Brent Beaven, the official who led the team at the site.

Pilot whales are about 13ft to 20ft (four metres to six metres) long and are the most common species of whale in New Zealand waters.

Whale strandings are common in New Zealand. Last month, 24 pilot whales died after becoming stranded in the North Island. In December 2009, more than 120 whales died in two separate beachings near Golden Bay and on the east coast of the North Island.