New Zealand authorities were mobilized on Monday to try to rescue dozens of “pilot dolphins” stranded on a beach in the far north of the South Island, a place where groups of pilot whales frequently wash up.

The Department of Conservation (DOC) said 49 mammals were discovered Monday morning on the sandy-tongued Farewell Spit, 90 kilometers north of Nelson City.

The DOC said that as of Monday afternoon, at least nine pilot whales had died and about 60 people were working to keep others alive in the hope that they could get out of the sea.

A DOC spokesman said, “Experts of marine mammals will participate in the beach reflecting operation and their care, trying to keep them in an environment of freshness and humidity.”

Farewell Spit is a 26 km long sand spit in Golden Bay.

It has been the scene of about ten cases of a group of pilot whales in the last 15 years. In February 2017, about 700 of these mammals were trapped in a farewell spit, including 250.

There is no definite scientific explanation for this phenomenon.

There are hypotheses about problems related to disease, navigation errors, presence of predators, extreme weather conditions or topography of some locations.

But others implicate specific disturbances caused by human activity and high-frequency sonars.