Around 2,500 dead seals were found off the Russian coast of the Caspian Sea, officials said Sunday.
The cause of the stunning mass death was unclear, authorities in the Russian province of Dagestan said, speculating it was likely due to natural causes.
Initial regional reports Saturday said 700 dead seals were found off the coast before the number later ballooned to 2,500, according to the Russian Ministry of Natural Resources and Environment.
In a statement, Zaur Gapizov, head of the Caspian Environmental Protection Center, said the seals were likely dead for a couple weeks. There was no sign they were killed or tangled up in fishing nets, he said.
Federal Fisheries Agency experts and prosecutors examined the coastline and collected data for lab research, which did not immediately spot any pollutants.
Mass seal deaths connected to natural causes are not unheard of.
Kazakhstan, which has a long Caspian coastline, reported there were at least three similar incidents this year.
The number of seals in the Caspian range from about 70,000, according to the Caspian Environmental Protection Center, to as much as 300,000, the fisheries agency has reported.
With Post wires