After several days of investigation, the U.S. Navy believes an urgent warning about an incoming missile aboard a destroyer Saturday night may have been a false alarm, defense officials said Tuesday.



The guided-missile destroyer Mason, underway in the Red Sea off the coast of Yemen, detected a "possible inbound missile," prompting the ship’s commander to activate the missile defense system and launch interceptor missiles, defense officials said.



Navy Capt. Jeff Davis, a Pentagon spokesman, said the commander’s decision to fire the missile defense system was "appropriate," but there has been no confirmation of an inbound missile posing a threat to the U.S. ship.



"We have not actually confirmed that that happened," Davis said Tuesday.



"We are not ready to call it an 'attack'," he said. "We are going back and reviewing the information to see what happened."



The incident underscores the heightened tension in the Red Sea after two confirmed missile attacks on U.S. ships last week came from territory in Yemen that is controlled by the Iran-backed Houthis rebels.



Military officials use an array of sensors to investigate possible missile attacks, including radar systems from other U.S. ships in the area, U.S. aircraft overhead and satellite imagery.



"We look at a lot of different points of information. It’s not just one single ship and one single radar system," Davis said.



The two confirmed attacks, on Oct. 9 and Oct. 12, were the first known instances of a U.S. Navy ship engaging its Standard Missile-2 air defense system outside of training situations. The SM-2 system uses interceptor missiles to destroy incoming missiles at long-range by either striking them or detonating nearby and knocking them off course. The SM-2 is used before last-resort self-defense systems, like the shorter-range Sea Sparrow missiles.



On Thursday, the destroyer Nitze fired Tomahawk missiles into southern Yemen, where the cruise missile attacks originated. The U.S. rockets destroyed three radar sites in the area controlled by Houthis rebels, who receive support from Iran. The coastal radar systems provided key targeting data to the cruise missiles fired from Houthis-controlled area.



The U.S. ships were in international waters at least 11 miles from the coast.



Cruise missiles can travel at about 600 miles per hour, giving U.S. ships between one and two minutes between detection and possible impact.



Many experts believe the cruise missiles may have come from Iran.



The recent attacks from the Red Sea will likely make thousands of sailors eligible for Combat Action Ribbons, a citation the Navy has not bestowed on the crew of a ship in international waters since the Gulf War in 1991.





