( CNN ) -- The U.S. Coast Guard is searching off the coast of Puerto Rico for a Canadian who witnesses say jumped off a cruise ship Saturday night . The FBI is investigating why Tien Phuoc Nguyen , 26 , jumped overboard while on a cruise with his family , a Coast Guard news release said Sunday . Adventure of the Seas , a Royal Caribbean International cruise ship , was about 15 miles east of Mona Island , Puerto Rico , when Nguyen jumped into the water , the Coast Guard said . A Coast Guard MH-65 Dolphin helicopter and the Coast Guard Cutter Cushing were sent to the area to search late Saturday . The cruise ship , which was sailing to San Juan , immediately turned around to search for the missing passenger , a statement from Royal Caribbean International said . `` A review of the ship 's closed-circuit camera footage observed the guest going overboard , '' the cruise line said . `` The location of the ship at the time the guest went overboard was marked on the ship 's Global Positioning System and the ship , along with the Coast Guard , conducted a search for the missing guest . '' The cruise to San Juan resumed Sunday morning , leaving the search to the Coast Guard , the statement said . The Adventure of the Seas was near the end of a weeklong cruise that began in San Juan . CNN 's Janet DiGiacomo contributed to this report .
He wondered why Tien and Nguyen , vacationing with friends , jumped off cruise ship . Time of the day was about 15 miles east of Mona ##gas , Puerto Rico . They went overboard near the end of a weeklong cruise .