The major oil spill off the southern coast of Russia killed over 15,000 birds and poisoned over 20,000, the state agricultural and natural resources monitoring agency has confirmed.

“It is impossible to determine the exact number of perished birds due to the fact that the dead birds were swept to the beach and covered by some 50-centimeter layer of a shell-and-oil mixture,” the agency said.

“Oil poisoning was registered in now surviving 19,500 bald coots, 21 grebes, some 350 ducks, and 755 cormorants, and the possibility that they may die is very high,” the agency warned.

The economic damage is now estimated at $267 million, with Russian officials saying that shipping could be limited to barges under 25 years ways because of the disaster .