The footage was posted Monday on the website of Iran's semi-official Fars news agency. In what appear to be staged shots, it shows several crew members in various locations around the tanker.
The crew can be seen talking in a meeting room, operating the ship's systems and cooking in the vessel's kitchen. A spokesperson for Stena Bulk, the company that operates the tanker, told CNN that they could not verify the authenticity or the source of the video.
While the vessel was sailing under a UK flag, Stena Bulk is headquartered in Sweden, and the 23 seafarers on board hail from India, Latvia, Philippines and Russia.
The family of Dijo Pappachan, one of the Indian nationals on board, told CNN they have not had any contact with him since Friday.
Pappachan's cousin, Joseph Vincent, said Pappachan called his family on Friday and spoke to his mother for about one hour. On Saturday morning, Stena Bulk's head office in Mumbai informed the family that he was on the captured ship.
Stena Bulk said it was in contact with both the UK and Swedish governments and that local staff in the crew's four home countries were "in constant touch with the families" of the crew and will "continue to do everything humanly possible to keep them informed and to support them in every way we can."
In an exclusive interview on Monday, the company's CEO Erik Hanell told CNN that Iranian authorities are still not communicating with them, but they have heard indirectly that the crew is in good health "considering the circumstances."
He added that they not spoken to the crew directly.
What we know
The capturing of the tanker marked another escalation in the tense standoff between Iran and Western powers following US President Donald Trump's decision to withdraw from the Iran nuclear deal last year.
The UK was a party to the 2015 agreement that curbed Iran's nuclear program in exchange for sanctions relief. The British government has made attempts to save the deal alongside France and Germany, the two other European signatories.
But following the tanker's capture, the UK warned Iran that it would take "robust" action in response to the incident.
Iran's elite Islamic Revolutionary Guard Corps -- whose troops captured the ship -- accused the vessel of "violating international regulations."
However, Hanell told CNN that "there's nothing that shows us that we have been violating any kind of laws." And the UK has said the Stena Impero was within Omani territorial waters exercising "the lawful right of transit passage in an international strait."
The UK government's emergency response committee, known as COBRA, met on Monday to discuss the situation. Following the meeting, the UK Foreign Secretary Jeremy Hunt called the incident an act "of state piracy" and said the UK would take part in a Europe-led maritime protection mission in the Strait of Hormuz.
He added that it was with a "heavy heart" that the the Gulf would see an increased international presence, and that the UK does not seek confrontation with Iran.
The seizure of the Stena Impero came just hours after authorities in Gibraltar agreed to extend the detention of an Iranian oil tanker in its custody for 30 days.
That ship, the Grace 1, was seized by British authorities on July 4. It was accused of attempting to transport oil to Syria in violation of European Union sanctions.
"The Iranians likely see the seizure of the Stena Impero as payback," said Naysan Rafati, Iran analyst at the Crisis Group in Washington.
The tensions are also impacting oil prices, because the Strait of Hormuz plays a crucial role in the global oil shipping industry.
The channel, which is just 21 miles wide at its narrowest point, is the only way to move oil from the Persian Gulf to the world's oceans.
"That's why we're seeing calls to steps up maritime patrols and protect the hundreds of vessels that transit each month," Rafati said.
CNN's Melissa Bell, Shirzad Bozorgmehr, Nikhil Kumar and Chelsea J. Carter contributed reporting.
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