The crew of the seized tanker Stena Impero are safe, the vessel’s owners said, after direct communication with them in Iran.
The British-flagged vessel was taken by Iran’s Revolutionary Guard on Friday amid heightened tensions between Tehran and the West.
Stena Bulk confirmed it had now had direct contact with the crew of the impounded vessel.
The ship’s master said they were all safe and there had been good cooperation with the Iranian personnel on board.
Stena Bulk said the crew’s family members were being kept updated on the latest developments and being offered the firm’s full support.
Erik Hanell, president and CEO of Stena Bulk said: “We do of course appreciate this step of development and that this is a first sign that we will soon see more positive progress from the Iranian authorities."
Footage shows a helicopter hovering over the vessel as people drop down onto the ship from a rope.
The development came as the head of the Iranian supreme leader’s office said the UK was sending a mediator to negotiate for the release of the vessel.
“A country that at one time appointed ministers and lawyers in Iran has reached a point where they send a mediator and plead for their ship to be freed,” Mohammad Mohammadi-Golpayegani said, according to the semi-official Tasnim news site.
The issue will be one of the first diplomatic challenges confronting incoming prime minister Boris Johnson.
Tehran has claimed the tanker collided with a fishing boat, while the UK has accused Iran of “state piracy”.
Meanwhile, a large British-flagged vessel has transited the Strait of Hormuz in the first such passage made by a UK ship since the seizure.
Maritime publication Lloyd’s List identified the ship as the BW Elm. It reported that the Royal Navy warship HMS Montrose closely shadowed the vessel, but did not provide a direct escort.
Data from the tracking site Marine Traffic showed the commercial ship arrived at a port in Qatar early on Wednesday after transiting the strait.
The ship’s owner BW LPG declined to comment on specifics, but said the company “is grateful for the UK and international community for their naval presence” providing security to ships in the area.