A U.S. military helicopter fired on the rudder of a Panama-flagged ship that was attempting to break a naval blockade of Iranian ports, The Wall Street Journal reported Tuesday, citing a U.S. official.

The incident occurred after the ship's crew reportedly ignored warnings from personnel enforcing the blockade.

Initial assessments from the British maritime risk management group Vanguard and a maritime security source suggested that the container ship Vela Nova may have been struck by a missile while traversing the Gulf of Oman. Reports indicated that the ship appeared to be attempting to transfer its crew to another civilian vessel following the attack. No casualties were immediately reported.

The U.S. military operation was aimed at enforcing a naval blockade of Iranian ports.