FORT CAMPBELL, Ky. (AP) — Investigators recovered "black boxes” from two U.S. Army Black Hawk helicopters that crashed last week in Kentucky, killing all nine soldiers aboard, the military announced Tuesday.

A U.S. Army aviation safety team from Fort Rucker, Alabama, found the flight data recorders, which are commonly referred to as black boxes in civilian aircraft, from the HH-60 Black Hawk helicopters, a news release from the 101st Airborne Division (Air Assault) said. The helicopters crashed near Fort Campbell during a nighttime training exercise on March 29. The recorders have been sent to Fort Rucker for further analysis.

“The duration of the investigation is determined by the thorough analysis of all factors,” division spokesman Lt. Col. Tony Hoefler said in the news release.

The pilots were using night-vision goggles during the exercise, Army officials said. Brig. Gen. John Lubas, the 101st Airborne deputy commander, has said the accident occurred while the helicopters were flying and not during a medical evacuation drill.

The soldiers’ remains have been taken to Dover Air Force Base, which is home to the Joint Service Mortuary Affairs Office, officials said.

Three of the soldiers killed in the crash were posthumously promoted to the next higher grade, officials said: Sgt. Emilie Marie Eve Bolanos, 23, of Austin, Texas; Chief Warrant Officer 3 Zachary Esparza, 36, of Jackson, Missouri; and Chief Warrant Officer 2 Aaron Healy, 32, of Cape Coral, Florida.

The others killed were Warrant Officer 1 Jeffery Barnes, 33, of Milton, Florida; Sgt. Isaacjohn Gayo, 27, of Los Angeles, California; Staff Sgt. Joshua C. Gore, 25, of Morehead City, North Carolina; Staff Sgt. Taylor Mitchell, 30, of Mountain Brook, Alabama; Chief Warrant Officer 2 Rusten Smith, 32, of Rolla, Missouri; and Sgt. David Solinas Jr., 23, of Oradell, New Jersey, the Army said.