With the detainment of tanker Stena Impero and its crew by the Iranian authorities having now reached 19 days, owner of the ship Stena Bulk said on Tuesday that the situation remains “unacceptable and unjustifiable”.

Erik Hanell, president and ceo of Stena Bulk, said: “We are maintaining limited communication with the crew onboard and although they remain in good health considering the circumstances, we continue to be concerned about their welfare given the amount of time they have been in confinement.”

Stena Bulk and Northern Marine Management are working with all the relevant authorities, including UK and other national governments, to secure the release of the 23 crew.

“This has included face to face meetings with senior government representation. We are confident this matter is being given the high priority level it warrants, and we will do everything possible to ensure the Stena Impero remains at the forefront of their agendas,” Hanell said.

“On behalf of Latvian authorities, a Finnish consulate visit to the Latvian crewmember onboard the vessel took place on Saturday 3 August. The Finnish representative advised that the crew were in good health, however the duration of their confinement remains of considerable concern to the crew. We welcome all support to the crew from national embassies,” he added.

Stena Bulk has yet to receive an official answer from the Iranian authorities regarding its request to attend the vessel.