Hundreds of swans have been found dead at a nature reserve in the Central Asian country of Kazakhstan, environmental officials said Tuesday. The nature reserve is based around Lake Karakol, near the shores of the Caspian Sea, and is home to a variety of rare and endangered species.

"Between 21 December and 8 January, a total of 675 swan carcasses were discovered on Lake Karakol," the Kazakh ecology ministry told AFP.

The birds may have died from avian flu, the ministry said, adding that specialists had been dispatched to the site to investigate.

Lake Karakol was artificially formed in the Soviet era near the site of a nuclear plant, and has been the focus of conservation efforts.

Activists have previously raised concern about environmental problems in western Kazakhstan, particularly air and water pollution.

Kazakh President Kassym-Jomart Tokayev called in 2022 for Lake Karakol to be preserved, describing it as a "unique reservoir." 

Avian flu that has impacted millions of poultry birds and thousands of wild birds has also killed a polar bear for the first time ever recorded, officials announced recently. The infected polar bear died sometime in the fall, and the cause of death was confirmed to have been the avian flu on Dec. 6, according to Alaska's Division of Environmental Health.

"This particular avian flu outbreak is of global scope," Clark told CBS News. "It has affected many species of birds and mammals worldwide: that scope is unprecedented. Each of those interactions with a new host species creates novel conditions for the virus, and in 2020 we all learned what that can mean."

The most recent avian flu outbreak has caused trouble worldwide. In its most recent situation report, published in October, the World Organization for Animal Health said that more than half a million poultry birds died or were culled globally in the most recent three-week period leading up to the report. In Argentina, 300 southern elephant seals died because of the virus.