Update: Officials say human remains have washed ashore, but that the search is still being treated as a search-and-rescue mission. Searchers are focusing their efforts on the Santa Rosa Sound, a narrow waterway separating Santa Rosa Island from Florida's mainland.

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Seven Marines and four soldiers are missing after an Army helicopter crashed off the Florida coast Tuesday night.

The UH-60 aircraft out of Eglin Air Force Base went down during a routine nighttime training mission along a beach between Pensacola and Destin. It was reported missing around 8:30 p.m. Tuesday, and crews began finding debris around 2 a.m. Wednesday. Officials say the area was under a fog advisory at the time of the crash.

According to the Associated Press, the missing Marines were part of a special operations group based in Camp Lejeune, North Carolina. The soldiers were with a National Guard unit from Hammond, Louisiana.

Search and rescue crews were still searching the area Wednesday morning, but thick fog continued to be a problem.