The Coast Guard was responding to a civilian helicopter with two people aboard, 60 miles south of Terrebonne Bay, Wednesday.
Watchstanders at Coast Guard Sector New Orleans received the report at 2:40 p.m., of a downed helicopter, Bell model 206-L4, containing two people aboard near an oil rig in the South Timbalier Block 317.
Crewmembers on the rig deployed a life raft and reported the aircraft sank below the water.
Sector watchstanders launched a MH-65 Dolphin helicopter crew from Coast Guard Air Station New Orleans, an HC-144 Ocean Sentry fixed-wing aircraft crew from Coast Guard Aviation Training Center Mobile, Alabama, and diverted the Coast Guard Cutter Sturgeon, an 87-foot patrol boat homeported in Grand Isle, Louisiana, to assist in the search. Two Good Samaritan vessels are aiding with the search.