Human remains have been found aboard a chemical tanker struck by a drone in Romanian territorial waters on October 15, with six of the crew feared dead.

The vessel, the Wine Trader, was flying a San Marino flag when it was hit about 24 kilometers southeast of Sulina at the mouth of the Danube. Seven of its 12 crew members were reported missing after the attack, while five were rescued. The ship was transferred to a shipyard in the Bulgarian port of Varna in early November for repairs.

Prosecutors in Varna announced on Saturday that workers found "very deteriorated human remains" during cleaning operations on board. DNA tests have been ordered to identify the victims. A Bulgarian law enforcement source told AFP that the condition of the remains makes it impossible to determine the exact number of bodies with certainty. The source said it is "very likely six" people. Investigations are underway in both Bulgaria and Romania.

The discovery comes as drone attacks on commercial shipping in the Black Sea have intensified. Since the beginning of October, at least nine commercial vessels have been struck by drones off the Romanian and Bulgarian coasts, leaving 34 people dead or missing in total.

The announcement precedes an official visit to the Black Sea region by European Commission President Ursula von der Leyen on November 9 and 10. She will travel to Bucharest on Monday and then to Varna on Tuesday, where she is scheduled to meet Bulgarian Prime Minister Rumen Radev and visit the Naval Academy.