A Liberian-flagged vessel that was hit by drones off Bulgaria’s Black Sea coast has sunk, the local maritime administration said Thursday.

Axar.az reports, citing The Associated Press, three maritime drones struck the container ship Contship Jet about 21 nautical miles off the coast of Bulgaria on Wednesday, Defense Minister Dimitar Stoyanov said. It was the fifth drone attack in the NATO country’s exclusive economic zone this month.

The Greek-managed container ship was en route from Israel’s port of Haifa to Constanța in Romania. All 18 crew members, 14 Filipinos and four Ukrainians, were rescued by Bulgarian naval and border police vessels and taken to the port city of Varna for medical checks.

Some of the containers on board were carrying lithium-ion batteries, flammable liquids, gases and other hazardous materials, the site maritime.bg reported. Navy teams reported no signs of pollution after taking samples from several locations in Bulgarian territorial waters.