The Marines suffered smoke inhalation and possible traumatic brain injuries, including concussion-like symptoms such as headaches, but were not seriously hurt and soon returned to duty, the officials claimed.

The incident adds to growing scrutiny over the Pentagon’s reporting of US military casualties during the war on Iran, which began in February.

According to the officials, seven of the Marines were enlisted personnel and one was an officer, and they were operating as part of a battalion landing team when the vessel was struck.

The vessel was not a US Navy ship, the officials said.

They declined to identify its specific type, describing it only as a maritime vessel.

Meanwhile, the US Defense Department did not disclose any Sept. 14 attacks on US forces in the region.

The Pentagon’s Defense Casualty Analysis System listed 861 US service members as injured in the war against Iran.

The eight Marines were added to the system nearly 10 days after the attack, without details about where, when or how they were injured.

One official attributed the delay to symptoms not always being reported immediately and to the system not updating in real time.

Reporting of US casualties has also been inconsistent during the war, with the Pentagon lowering its reported death toll over the summer after reclassifying how some US troops were killed.

More broadly, the United States has more than 50,000 service members deployed across the US Central Command area, including two carrier strike groups led by the USS George Washington and USS George H.W. Bush.

The US military continues to enforce an illegal naval blockade on ships entering or leaving Iranian ports.