The crew of a tanker seized by Iran’s navy this week in a row with the United States are safe, the vessel’s Greek owners said on Sunday.

Empire Navigation said in a statement that an associate had contacted Iranian authorities and reported that “all the crew members on board the St. Nikolas are safe and in good health.”

The company added that it had not been itself able to directly contact the 19-man crew of the Marshall Islands-flagged ship, which is anchored in the vicinity of the Iranian port of Bandar Abbas.

Eighteen Filipinos and a Greek are on board.

Iran said it had seized the ship off Oman on Thursday to retaliate for the “theft” of its oil from the same tanker — which at the time was called the Suez Rajan last year by the United States, state media said.

The United States condemned what it called an “unlawful seizure” and demanded Iran “immediately release the ship and its crew.”

Iran has responded with tit-for-tat measures in the past after seizures of Iranian oil shipments.

Crippling U.S. sanctions, reimposed following Washington’s 2018 withdrawal from a landmark nuclear deal, target Iranian oil and petrochemical sales in a bid to reduce Iran’s energy exports.

The vessel had been loaded with 145,000 tons of crude oil in Basra, Iraq, and was destined for Aliaga, Turkey, via the Suez Canal.

British maritime risk company Ambrey this week said the recently renamed tanker was previously prosecuted and fined for carrying sanctioned Iranian oil, which was confiscated by U.S. authorities.

In September, the United States said it had several months earlier seized the Suez Rajan and its cargo of 980,000 barrels of crude oil.

The U.S. Department of Justice said at the time that the oil on the Greek-managed tanker was allegedly being sold by Iran’s Islamic Revolutionary Guard Corps to China.

The Gulf of Oman, a key route for the oil industry that separates Oman and Iran, has witnessed a series of hijackings and attacks over the years, often involving Iran.

Shipping in the resource-rich region is also on heightened alert following weeks of drone and missile attacks in the Red Sea by Yemen’s Iran-backed Houthi rebels.