A tugboat moves cargo towards the Strait of Hormuz off the coast of Musandam province, Oman, July 20, 2018.
Panama's maritime authority announced on Saturday night that it had begun the process of withdrawing the registration of the MT Riah oil tanker, which was towed to Iran after disappearing from tracking maps in the Strait of Hormuz at the beginning of last week, Reuters reported.

An investigation determined that the tanker "deliberately violated international regulations" by not reporting any unusual situation, the authority said.

The Islamic Revolutionary Guard Corps (IRGC) said on Thursday July 18 that they had seized a foreign ship carrying one million liters of smuggled fuel south of Larak Island in the Persian Gulf on Sunday July 14, according to Fars News.

The foreign ship was seized by order of Iranian judicial authorities during an operation to monitor and control traffic in the Persian Gulf in order to detect and combat organized smuggling.

"We roundly condemn the use of Panamanian flagged ships for illicit activities," said the statement from Panama's maritime authority.

It is still unclear which country or company owns the Riah, according to Reuters.

The ship had a capacity of two million liters and had 12 foreign crew members, according to Fars.

"We're seeking further information following reports of a tanker seized in the Gulf. We continue to urge the Iranian authorities to de-escalate the situation in the region," a British government spokeswoman said.

"We are continuously monitoring the security situation there and are committed to maintaining freedom of navigation, in accordance with international law."

On Wednesday, US officials said they believe that the Panama-flagged tanker MT Riah was seized by the IRGC on Saturday night, when it was crossing the Strait of Hormuz in international waters, CNN reported.

Information from the US intelligence agency indicated that IRGC troops forced the tanker to enter Iranian territorial waters before bringing the vessel to Iran's Qeshm Island.

Tracking data showed that the UAE tanker drifted off into Iranian waters after 11 p.m. on Saturday July 13 when it stopped transmitting its location, according to the Associated Press.

The Riah is a 58 meter (190 foot) oil tanker which usually traveled between Dubai and Sharjah on the UAE's west coast before going through the strait towards Fujairah on the east coast.

On Tuesday, a foreign ministry spokesperson announced that the UAE tanker was withdrawn to Iranian waters to receive assistance from Iranian forces after suffering from a technical issue, according to the Iranian ISNA news agency. The necessary repairs will be done to the vessel and further details will be announced later, according to the spokesperson.

Sources from the UAE reported the same to the US, according to the AP.

As of Wednesday, the crew had still not contacted their base in the UAE since the boat disappeared from radar on July 13, according to Radio Farda. Abbas Mousavi, the spokesman for Iran's Foreign Ministry, claimed that the tanker's crew had called for help following a technical problem and that Iranian forces had acted according to international regulations.

Radio Farda emphasized that the tanker disappeared from radar while sailing through the Straits of Hormuz on July 13, even though tankers usually have a backup generator or communications equipment in the case of an emergency, according to military analyst Hossein Arian.

An official from the UAE told Al Arabiya that the oil tanker is not owned or operated by the country and that it did not send a distress call.

"The tanker in question is neither UAE owned nor operated. It does not carry Emirati personnel and did not emit a distress call. We are monitoring the situation with our international partners," said the official.

The tanker had not switched off its tracking throughout three months of trips around the UAE, Capt. Ranjith Raja of the data firm Refinitiv told AP. "That is a red flag," said Raja.

The ship that the IRGC announced on Thursday they had seized was the same one that they towed after a distress call at the beginning of last week, according to Reuters. On Friday, the IRGC announced that they had seized the British-flagged Stena Impero oil tanker.

British Defense Secretary Penny Mordaunt called the capture of the Stena Impero a "hostile act." Foreign Secretary Jeremy Hunt said he had expressed "extreme disappointment" by phone to his Iranian counterpart, Mohammad Javad Zarif. Britain also summoned the Iranian charge d'affaires in London.

A spokesman for the IRGC, Brig.-Gen. Ramezan Sharif, said Tehran had seized the Stena Impero in the Strait of Hormuz despite the "resistance and interference" of a British warship which had been escorting it. No British warship was visible in the video posted by the corps.

Iran's Fars News Agency said that the IRGC had taken control of the Stena Impero on Friday after it collided with an Iranian fishing boat, whose distress call it ignored.

The vessel, carrying no cargo, was taken to the Iranian port of Bandar Abbas. It would remain there with its 23 crew members - 18 of them Indians - while the accident was being investigated, Iranian news agencies reported, quoting Allahmorad Afifipour, head of the Ports and Maritime Organisation in southern Hormozgan province.