More than 200 pilot whales have died after being stranded on the shores of New Zealand's remote Chatham Islands, the New Zealand's Department of Conservation said on Saturday.

Conservation officers said in a statement that they could not actively refloat whales stuck on the island because of "the risk of shark attack to both humans and the whales themselves."

The Chatham Islands are about 785 kilometers (488 miles) east of New Zealand.

Mass strandings are reasonably common on the islands, though marine biologists are puzzled by the phenomenon and are not sure what causes it.

New Zealand has one of the world's highest rates of whale strandings, including in 2017, when over 400 whales died after stranding on Farewell Spit at the northern tip of South Island.

Around 1,000 whales died in mass strandings recorded back in 1918 on the Chatham Islands, making it one of the largest incidents ever, according to the Department of Conservation.

Tough conditions for rescuers

The pilot whales, members of the dolphin family, were reported to be in distress on the island on Friday, the department said.

"The Chatham Islands is a challenging spot for stranding response, known for great white sharks, remote beaches and a resident population of less than 800 people," said Project Jonah, an animal rescue charity group based in New Zealand.

According to the conservation department, some of the whales that survived were euthanized or humanely put down to prevent any suffering.

Local people were also present to lend support.

"All the stranded pilot whales are now deceased, and their bodies will be left to decompose naturally on site," the department said. 

Two week ago, almost 200 stranded whales died on a beach on the west coast of Tasmania, Australia, as well. 

rm/dj (dpa, Reuters)