U.S. Marines deployed from helicopters to search a cargo ship in the Arabian Sea before allowing it to continue its journey.

CENTCOM, the agency responsible for U.S. military operations in the Middle East, released images on April 28 of the landing and search of the cargo ship Blue Star III in the Arabian Sea. The vessel is suspected of being en route to Iran and violating a U.S. blockade.

In the video, soldiers from the 31st Marine Expeditionary Unit (MEU) are seen deploying by helicopter from the amphibious assault ship USS Tripoli, then rappelling down to the Blue Star III and accessing the control room.

"U.S. forces released the vessel after searching and verifying that it had no plans to dock in Iran," CENTCOM announced.

CENTCOM did not specify the reason why the ship was suspected of heading to Iran. Maritime tracking data shows the Blue Star III departed from the Pakistani port of Qasim and was en route to the Omani port of Sohar.

This is the fourth cargo ship inspected since the U.S. imposed a maritime blockade on Iran, but the first to be released. At least three ships, including the Touska, Tifani, and Majestic X, have been seized by U.S. forces.

US Marines approach a cargo ship in the Arabian Sea using speedboats. Photo: CENTCOM

CENTCOM said the blockade has forced 39 ships to change course over the past two weeks, stating that US forces will continue to enforce the blockade across the Middle East and asserting that the operation has "cut off all two-way trade with Iran."

The Strait of Hormuz is a strategic shipping lane, transiting approximately 20% of the world's oil and gas supply. Iran has virtually blockaded the strait, forcing commercial ships to seek permission or pay fees to pass through and banning vessels linked to the US and Israel, as well as other parties involved in the conflict.

Meanwhile, the US Navy is enforcing a blockade outside the Gulf of Oman, warning it will seize any ship arriving at or departing from Iranian ports, as well as those that have paid fees to Tehran.

Location of Iran and the Arabian Sea. Graphic: Guardian

The US has also expanded the scope of its blockade, as well as the types of goods that could be subject to inspection or seizure if linked to Iran.

Some maritime experts believe controlling the entire flow of ships through the Strait of Hormuz is a major challenge, and suggest that ships could evade it by altering their navigation data or moving through the waters of other countries.