Around 1,700 seals have been found dead on the Caspian Sea coast in southern Russia, according to officials.
Their cause of death so far remains unclear, but authorities in the Russian province of Dagestan said the animals had likely died of natural causes.
On Saturday, regional officials initially said 700 seals had been discovered dead on the coast.
But Zaur Gapizov, head of the Caspian Environmental Protection Centre, said on Sunday that following a broader inspection of the coast, the number of dead seals was in fact 1,700, the RIA Novosti news agency reported.
He said the seals were believed to have died a couple of weeks ago, and added there were no signs they had been killed by poachers.
Federal Fisheries Agency experts, along with prosecutors, inspected the coastline and collected data for laboratory research, which did not uncover any pollutants.
Several incidents of mass seal deaths in previous years have been attributed to natural causes.
The data about the number of seals in the Caspian varies, but the fisheries agency claims it is between 270,000 and 300,000, while Mr Gapizov's centre puts the number at 70,000.