An oil tanker sought by the U.S. over allegedly circumventing sanctions on Iran was hijacked on July 5 off the coast of the United Arab Emirates, a seafarers organization said Wednesday.

Satellite photos showed the vessel in Iranian waters on Tuesday and two of its sailors remained in the Iranian capital.

It wasn't immediately clear what happened aboard the Dominica-flagged MT Gulf Sky, though its reported hijacking comes after months of tensions between Iran and the U.S.

David Hammond, the CEO of the United Kingdom-based group Human Rights at Sea, said he took a witness statement from the captain of the MT Gulf Sky, confirming the ship had been hijacked.

Hammond said that 26 of the Indian sailors on board had made it back to India, while two remained in Tehran, without elaborating.

“We are delighted to hear that the crew are safe and well, which has been our fundamental concern from the outset," Hammond told The Associated Press.

Hammond said that he had no other details on the vessel.

TankerTrackers.com, a website tracking the oil trade at sea, said it saw the vessel in satellite photos on Tuesday in Iranian waters off Hormuz Island. 

The Emirati government, the U.S. Embassy in Abu Dhabi and the U.S. Navy's Bahrain-based 5th Fleet did not respond to requests for comment. Iranian state media did not immediately report on the vessel and Iran's mission to the United Nations did not immediately respond to a request for comment.

In May, the U.S. Justice Department filed criminal charges against two Iranians, accusing them of trying to launder some $12 million to purchase the tanker, then named the MT Nautica, through a series of front companies. The vessel then took on Iranian oil from Kharg Island to sell abroad, the U.S. government said.

Court documents allege the scheme involved the Quds Force of Iran's paramilitary Revolutionary Guard, which is its elite expeditionary unit, as well as Iran's national oil and tanker companies. The two men charged, one of whom also has an Iraqi passport, remain at large.

Data from the MT Gulf Sky's Automatic Identification System tracker shows it had been turned off around 4:30 a.m. July 5, according to ship-tracking website MarineTraffic.com. Ships are supposed to keep their AIS trackers on, but Iranian vessels routinely turn theirs off to mask their movements.