CNN
 — 

Around 700 endangered seals have been found dead on Russia’s Caspian coast in the North Caucasus, local officials said Sunday.

Caspian seals, the only mammals found in the Caspian Sea, have been classified as endangered on the International Union for Conservation of Nature (IUCN) red list since 2008.

“The number of discovered animals may increase. The cause of death has yet to be determined,” the press service for the region’s fisheries agency said, according to Russian state media outlet TASS.

The seals washed up on the coast of Russia’s republic of Dagestan, along the Caspian Sea, the largest landlocked body of water in the world.

TASS said “researchers had already started working on identifying the cause of the mammals’ deaths.”

The news comes after more than 140 Caspian seals were found dead on Kazakh beaches of the Caspian Sea earlier this year, according to KASPIKA, an agency for the conservation of Caspian seals.

According to the IUCN, the Caspian seal population has suffered from over-hunting, habitat degradation and climate change.

The Caspian Sea is bordered by five countries: Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan.