Romania is investigating a possible new drone attack on a tanker off the country’s Black Sea coast.

Late on Wednesday, Romanian rescue teams reached a Comoros-flagged vessel near the border with Ukraine. The crew had managed to extinguish a fire, and Defense Minister Radu Miruta states that authorities are investigating whether the ship was attacked by a drone.

Suspected Russian drones have struck several vessels off the coasts of Romania and Bulgaria since last week.