Dozens of crew members have been rescued after abandoning two oil tankers hit by explosions in the Gulf of Oman.
Ship operators said 21 crew on board the Kokuka Courageous and 23 on the Front Altair had been evacuated.
Iran rescued the 44 after an “accident”, state media said, although the cause is unconfirmed. The United States Navy said it received two distress calls.
The incident comes a month after four oil tankers were attacked off the United Arab Emirates (UAE).
The UAE blamed an unnamed “state actor” for those attacks, which involved naval mines. The US said Iran was behind the attacks, an accusation Tehran denied.
The attacks increased long-standing tensions between Iran and the US and its allies in the Gulf.
Oil prices rose as much as 3.9% from a near five-month low following Thursday’s incident, Bloomberg reports.
Josh Frey, of the 5th Fleet, based in Bahrain, said in a statement: “US naval forces in the region received two separate distress calls at 06:12 local time (03:12 GMT) and a second one at 07:00.”
He said the USS Bainbridge was assisting.
The UK Royal Navy-linked UK Maritime Trade Operations (UKMTO) safety group earlier issued a warning, urging “extreme caution” in the area.
Iran’s IRIB news agency tweeted an image of what it said was the ablaze Front Altair, although the picture has not been independently verified.
Wu I-fang, a spokesman for Taiwan’s state oil refiner CPC Corp, which chartered the Front Altair, said it was carrying 75,000 tonnes of naphtha and was “suspected of being hit by a torpedo”, although this has not been confirmed.
He said all the crew had been rescued from the Marshall Islands-flagged vessel. The ship’s owner, Norwegian firm Frontline, said the vessel was on fire.
The operator of the Panama-flagged Kokuka Courageous, BSM Ship Management, said its crew abandoned ship and were rescued by a passing vessel.
The tanker was carrying methanol and was not in danger of sinking, a spokesman said. It is currently located about 80 miles from Fujairah in the UAE and 16 miles from Iran.
Iran state media said the rescued crew members had been taken to the port of Jask.