U.S. expands Iranian port blockade to include sanctioned ships "and vessels suspected of carrying contraband"

U.S. Naval forces will now board sanctioned ships "and vessels suspected of carrying contraband," regardless of their location in the waters around Iran, Naval Forces Central Command (NAVCENT) said Thursday, after a number of U.S.-sanctioned ships were tracked entering the Strait of Hormuz despite the ongoing blockade of Iranian ports.

In an update published Thursday, first shared by the U.K. Maritime Trade Operations Center, NAVCENT said all Iranian vessels, vessels with active sanctions, and those suspected of carrying contraband will be subject to interdiction, search and seizure regardless of their location in the Arabian Gulf, Strait of Hormuz, Gulf of Oman and Arabian Sea. 

The list of contraband includes petroleum, oil and lubricants that the Navy says are key to Iran's military operations and sustaining its war-time economy. 

It came after CBS News tracked two Iran-flagged container ships and multiple tankers under active U.S. Treasury sanctions transiting the Strait of Hormuz on Wednesday. The ships were visible on open-source tracking websites. Data from the tracking website MarineTraffic.com showed at least one sanctioned crude oil tanker that made the journey had previously called at Iranian ports. 

Any ships calling at Iranian ports can be stopped under the terms of the U.S. blockade, but the Pentagon has said American forces will not impede freedom of navigation for vessels transiting the Strait of Hormuz to and from non-Iranian ports. 

The U.S. Navy said Wednesday that it had turned back 10 Iranian-flagged oil tankers attempting to evade the blockade.  

Thursday's update means some ships that entered the Persian Gulf after the blockade began on Monday could now be stopped and searched by U.S. forces if they attempt to exit the strait again. One sanctioned crude oil tanker that entered the Gulf Wednesday has since turned off its transponder multiple times near Iran's Kish Island, possibly indicating it intends to call at an Iranian port.

Ships can turn off their AIS transponders, or even broadcast false locations to conceal their true whereabouts.