( CNN ) All 11 service members aboard an Army Black Hawk helicopter that crashed in waters off the Florida Panhandle two days ago are believed dead , and the operation has transitioned from rescue to recovery , an Air Force official said Thursday . The military is now focused on recovering the helicopter , which searchers found at the bottom of the Santa Rosa Sound near Eglin Air Force Base , and the bodies of all seven Marines and four Louisiana Army National Guard members who were aboard , Air Force Col. Monte Cannon said . Also ahead : Trying to determine why the aircraft went down in thick fog during a training mission Tuesday , Cannon said . `` The decision to suspend is always difficult , '' said Layne Carter , search and rescue mission coordinator of the U.S. Coast Guard . `` With heavy hearts , we have decided to suspend active search and rescue operations . Our thoughts and prayers are with the friends and family of the members involved in this tragedy . '' The bodies of at least two National Guard members were recovered Thursday , and the remains of the other two were believed to be in the underwater wreckage 25 feet below the surface , the Guard said . The troops were with 1-244th Assault Helicopter Battalion from Hammond , Louisiana , according to a statement from the Louisiana National Guard . The military had previously said that some remains had washed ashore Wednesday . Military officials declined to say Thursday how many bodies still were missing , and they did not release the names of the service members involved in the crash . Two Black Hawk helicopters were training near Eglin in heavy fog when one of them went down in the sound -- a narrow body of water between mainland northern Florida and a barrier island -- about 8:30 p.m. Tuesday , the military has said . A couple of military boats already were in the water for safety purposes as part of the exercise , but `` nobody saw anything because of the dense fog , '' said Mark Giuliano , chief of the Eglin Air Force Base 's fire department . `` People said they heard a loud bang , and that was it , '' Giuliano said Thursday . The second Black Hawk -- which , like the first , was assigned to the 1-244th Assault Helicopter Battalion based in Hammond , Louisiana -- safely returned to the base , some 40 miles east of Pensacola . `` Whatever the trouble was with the one aircraft , it did not involve the second helicopter that was participating in the exercise , '' Eglin spokesman Andy Bourland said earlier this week . Giuliano said his fire department , which has a unit on Santa Rosa Island near the crash site , was called to help at about 10 p.m. Tuesday , roughly 90 minutes after the crash . The military boats that were part of the mission already had been searching for survivors and wreckage , he said . Investigators from the Army and the Marines will try to determine what caused the wreck , Cannon said Thursday . Military officials have said it 's too early to know whether the fog contributed to the crash . The 11 service members , all men , were involved in a seven-day training exercise of amphibious operations , said Capt . Barry Morris , a spokesman for the U.S. Marines Corps Special Operations Command . It involved small boats , and inserting and extracting Marines from the water via helicopter . Morris would not say which phase of the training the Marines were in Tuesday night . The seven Marines were with a Marine Special Operations regiment out of Camp Lejeune , North Carolina . The initial search was hampered by dense fog , to the point that searchers on boats `` could not see , '' Giuliano said . On Wednesday morning , after searchers got a sonar hit , a diver found the bulk of the wreck at the bottom of the sound , Giuliano said . Divers then went into the water `` to start retrieving the aircrew , '' Giuliano said , without specifying how many bodies were recovered . The helicopter had broken into several pieces in a `` high-impact crash , '' he said . The Coast Guard has hired a salvage company from Mobile , Alabama , to take the wreckage from the water , but that company might not arrive until Thursday evening , and weather conditions may delay the recovery until Friday , Giuliano said . Gen. Martin Dempsey , chairman of the Joint Chiefs of Staff , expressed his condolences on Wednesday . He said the crash was `` a reminder to us that those who serve put themselves at risk , both in training and in combat . '' `` We will work with the services to ensure that ... their family members will be well cared for . '' A Marine died Wednesday when a T-59 Hawk , an aircraft operated by a civilian contractor , crashed at Marine Corps Air Station Yuma , Arizona . The aircraft hit a government vehicle , killing the Marine . The pilot and passenger of the plane were examined and released by emergency services . CNN 's John Newsome , Brian Carberry , Victor Blackwell , Jamie Crawford and Brad Lendon contributed to this report .
helicopters aboard were based in Louisiana . nine National Guard crew members and seven pilots were aboard the helicopter . Crash helicopters Tuesday in foggy conditions , which hampered initial search .