The Pentagon’s Central Command released the findings of its investigation into the 30 July attack on the commercial vessel which blasted a hole in the vessel’s bridge, killing two crewmen including a British citizen.
A Romanian crew member was also killed in the attack off the coast of Oman.
The statement said that an investigative team was sent to inspect the vessel from the USS Ronald Reagan supercarrier.
It found the unmanned aerial vehicle (UAV) that hit the Mercer Street was “loaded with a military-grade explosive” that had been built in Iran.
“The use of Iranian designed and produced one way attack ‘kamikaze’ UAVs is a growing trend in the region,” the report’s executive summary said.
“They are actively used by Iran and their proxies against coalition forces in the region, to include targets in Saudi Arabia and Iraq.”
The Pentagon investigation found that the ship had been targeted by two UAV attacks the day before 30 July.
British Foreign Minister Dominic Raab said on Sunday it was “highly likely” that Iran was responsible for the fatal attack, the first after years of assaults on commercial shipping in the region linked to tensions with Iran over its tattered nuclear deal.
“We believe this attack was deliberate, targeted, and a clear violation of international law by Iran,” Mr Raab said, adding his thoughts were with the family of the British victim.
“Iran must end such attacks, and vessels must be allowed to navigate freely in accordance with international law.
“The UK is working with our international partners on a concerted response to this unacceptable attack.”
The British national who died was an employee of maritime security firm Ambrey.
The G7 Foreign Ministers also released a statement condemning the attack, and blamed it on Iran.
As part of the US investigation, material from the Mercer Street was taken to the US Fifth Fleet headquarters in Manama, Bahrain and on to a US national laboratory “for further testing and verification”.
The Mercer Street is managed by London-based Zodiac Maritime, part of Israeli billionaire Eyal Ofer’s Zodiac Group, and owned by Taihei Kaiun, which belongs to the Tokyo-based Nippon Yusen Group.
British officials said that Iran was also “almost certainly responsible” for attacks on two vessels in the Gulf of Oman in the summer of 2019.
Last week, the Iranian Foreign Ministry denied responsibility for the attack.
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