DUBAI, United Arab Emirates (AP) — Satellite images released on Thursday show that a once-detained Iranian-flagged oil tanker sitting off the coast of Syria has been approached by a smaller Iranian tanker, an indication the ship could be preparing to transfer its cargo.

Images released by Maxar Technologies show the Jasmine alongside the Adrian Darya 1 on Wednesday, with mooring lines between them and a crane deployed on the larger vessel.

The Adrian Darya 1, formerly named the Grace 1, was detained off the British overseas territory of Gibraltar in July while carrying $130 million in crude oil, on suspicion of breaking European Union sanctions by taking the oil to Syria. Gibraltar later released the tanker, after it said Iran promised the ship wouldn't go to Syria.

The ship later sailed toward the Syrian coast, angering Britain.

The oil shipment website TankerTrackers.com said on Twitter on Tuesday that the Adrian Darya 1 was “postured in an STS (Ship-to-Ship) formation with a smaller Iranian-flagged Handymax (350K barrel capacity) tanker,” the Jasmine. It noted this was “not a confirmation of any oil transfer just yet. We'll compare imagery later.” The image it posted showed the two vessels off the coast of Syria.

However, the website said on Wednesday it was ending its public coverage of the Iranian tanker’s movements due to a tweet by U.S. Secretary of State Mike Pompeo, who used the image of the two tankers in a tweet of his own.

Pompeo tweeted that despite Foreign Minister Mohammad Javad “Zarif’s promise to the UK that the #AdrianDarya1 would not deliver oil to Syria, it is now transferring oil off the Syrian coast. Will the world hold Iran accountable if this oil is delivered to Syria?”

There was no official reaction from Iranian authorities.

Tension has been high between Tehran and Washington following President Donald Trump's decision over a year ago to unilaterally pull out of a nuclear deal between Iran and world powers. The U.S. has imposed sanctions that have kept Iran from selling its oil abroad and have crippled its economy. Iran has since begun breaking terms of the deal.

The tensions have led to the seizure of ships at sea. After the seizure of the Iranian-flagged tanker off the coast of Gibraltar, Iran seized the British-flagged oil tanker Stena Impero in July as it passed through the Strait of Hormuz, the narrow mouth of the Persian Gulf through which 20% of all traded oil passes.

Iranian authorities released the Stena Impero last Friday.