A cargo ship operated by Israeli shipping company ZIM has sunk in the Black Sea after being struck by at least three drones while sailing from Israel to Romania, with all 421 containers and their cargo lost at sea.

The CONTSHIP JET container ship, sank after being severely damaged by three drones about 17 nautical miles (31.5 kilometers) from Cape Kaliakra, within Bulgaria’s exclusive economic zone (EEZ), on Thursday, the daily newspaper Israel Hayom reported.

The cargo ship was en route from the Israeli regime’s port city of Haifa to the Romanian port of Constanta when the attack occurred outside Bulgaria’s territorial waters, the report said, adding that it was carrying various items, including lithium-ion batteries, corrosive liquids and acids, among other materials.

All 18 crew members, 14 Filipinos and four Ukrainians, were rescued and safely brought to the Bulgarian port of Varna.

Bulgarian Chief of Defense Admiral Emil Eftimov said the country had been unable to destroy the sea drones that attacked the ship.

He cited legal constraints, as the incident took place within Bulgaria’s exclusive economic zone rather than its territorial waters, as well as adverse weather conditions, as reasons for the failure to intercept the drones.

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Based on its design, the sea drone appears to be a previously undisclosed model, with no public sightings reported in the Black Sea before this incident, Israel Hayom reported, citing regional sources.

Bulgarian sources also reported that a French surveillance aircraft had been tracking the operation.

Drone strikes have targeted at least six vessels off the Bulgarian coast this month, with around 24 crew members feared dead, Reuters reported on Thursday, citing government statements.