In a video call with CEO of Ports and Maritime Organization of Iran Mohammad Rastad, the South Korean chief of IMO said he will be conducting necessary investigations into the case on the basis of conventions and regulations, according to Tasnim News Agency.

Iran has sent a tanker flotilla carrying 1.5 million barrels of gasoline to Venezuela. So far, four out of five tankers have reached the Venezuelan ports.

The US had threatened to take action against the Venezuela-bound tankers and had even dispatched a naval flotilla to the Caribbean Sea.

On May 17, Iranian Foreign Minister Mohammad Javad Zarif sent a letter to UN Secretary-General Antonio Guterres, warning about the US interference in the issue.

Seeking to deter further shipments of Iranian fuel to Venezuela, the Trump administration has also quietly warned foreign governments, seaports, shipping companies and insurers that they could face stiff US sanctions if they aid the tanker flotilla, the US envoy on Venezuela told Reuters on Friday.

Elliott Abrams, Washington’s special representative on Venezuela, said the pressure campaign targeting heavily sanctioned US foes Iran and Venezuela was being waged “to be sure everyone recognizes this would be a very dangerous transaction to assist.”

The Venezuelan Navy on Thursday escorted the fourth tanker bringing Iranian fuel through its waters to the gasoline-starved country, defying US threats of “measures” in response to the shipments. At least one other tanker was en route in the Atlantic.

It was a sign of deepening ties between Venezuela and Iran, both OPEC members with fraught relations with the United States.

The government of Venezuelan Socialist President Nicolas Maduro has flaunted the tankers’ arrivals to show it remains unbowed by pressure. The United States, which seeks Maduro’s ouster, has called it a “distraction.”

“We’ve alerted the shipping community around the world, ship owners, ship captains, ship insurers, and we’ve alerted ports along the way between Iran and Venezuela,” Abrams said in an interview.

He said diplomatic warnings, known as demarches, have been sent privately to governments “around the world.”

A person familiar with the matter said among them was Gibraltar, situated on the tankers’ route. A US official said various countries had been asked to deny then port services.

It remained unclear what impact this effort might have.