Experts from the Black Sea Basin Directorate and the Executive Environment Agency are taking seawater samples at five sites along the coast today, the Environment Ministry said. The sites are Durankulak, Shabla, Cape Kaliakra, Byala and Sozopol.

The checks follow an attack on a container ship carrying lithium-ion batteries. Three drones hit the vessel around noon yesterday, 17 nautical miles off Cape Kaliakra. More than 20 containers fell into the sea, some of them holding hazardous substances.

Earlier on this story: More than 20 containers fell into the sea from a ship hit off Cape Kaliakra

All 18 crew members were rescued.

Environment Agency labs in Varna and Burgas will test the samples for oil products, polychlorinated biphenyls (PCBs), metals and other physical and chemical indicators. The tests will show whether the water is polluted or its quality has changed in ways the eye cannot see.

The Defence Ministry also took samples yesterday from two points in territorial waters.

Water will also be taken near the container ship itself, and the results will go to the Environment Agency labs. The Environment Ministry said it will make the results public.