Seven Marines and four soldiers aboard a U.S. Army helicopter that crashed over waters off Florida during a routine night training mission were presumed dead Wednesday, and crews found human remains despite heavy fog hampering search efforts, military officials said.A Pentagon official said all 11 service members were presumed dead and that the Coast Guard found debris in the water. The official spoke to The Associated Press on condition of anonymity because the official wasn't authorized to speak on the record.Crews had found some human remains but still considered it a search-and-rescue mission, said Michelle Stewart, a military spokeswoman for Eglin Air Force Base.The helicopter a UH-60 Black Hawk from the Army National Guard was reported missing around 8:30 p.m. Tuesday, and search-and-rescue crews found debris around 2 a.m., said Andy Bourland, a spokesman for the base.Much of the area was enveloped in fog from Tuesday evening to Wednesday morning, said Katie Moore with the National Weather Service.Local law enforcement agencies vehicles gathered Wednesday at the crash scene, near a remote swath of beach owned by the military and used for test missions.From the beach, search boats could be heard blasting their fog horns as they combed the water, but could not be seen through the fog.Base officials said the Marines were part of a Camp Lejeune, North Carolina-based special operations group. The soldiers were from a Louisiana-based National Guard unit.Bourland said the Army helicopter took off from a nearby airport and joined other aircraft in the training exercise.The training area includes pristine beachfront that has been under the control of the military since before World War II.Test range manager Glenn Barndollar told The Associated Press in August that the beach provides an ideal training area for special operations units from all branches of the military to practice over the water, on the beach and in the bay.The military sometimes drops trainees over the water using boats or helicopters and the trainees must make their way onshore.