Russia declared a federal emergency on Thursday over an oil spill caused by two Russian tankers in the Black Sea, the Emergencies Ministry said. The tankers were hit by a storm on Dec. 15. One split in half and the other ran aground.

Volunteers are grappling with environmental havoc across more than 35 miles of coastline, after at least 3,700 tons of heavy oil spilled into the Kerch Strait.

Hundreds of volunteers and emergency workers continued to clean the coastline of Russia’s southern Krasnodar region Wednesday after two Russian ships spilled around 3,700 tons (3,300 tonnes) of low-grade fuel oil into the Kerch Strait.