Search and rescue teams are looking for 11 service members who went missing after their UH-60 Black Hawk helicopter crashed near Eglin Air Force Base, Florida, US.
The Louisiana National Guard said in a statement that the helicopter was carrying four army soldiers and seven marines, and went down near Eglin range site A-17, east of the Navarre Bridge,
Assigned to the 1-244th Assault Helicopter Battalion, it was one of two Black Hawks participating in a routine night-time exercise involving the Marine Special Operations Regiment from Camp Lejeune, North Carolina.
The second helicopter and its personnel returned safely, the statement added, noting that the debris from the aircraft was later discovered by a search and rescue team.
US Marines Corps Special Operations Command spokesman captain Barry Morris said the training involved insertion and extraction missions using small boats and helicopters to get soldiers in and out of a target site.
Louisiana National Guard adjutant general major general Glenn Curtis confirmed that the second Black Hawk returned to the base because of bad weather.
Curtis said: "One of them started to take off and then realised there was a weather condition and turned around and came back," .
According to the army, the downed helicopter was equipped with a flight data recorder, which could be recovered and will help investigators determine what caused the accident.
The names of the crew are being withheld pending next-of-kin notification.
Image: A Louisiana Army National Guard UH-60 Black Hawk helicopter performs sling-load operations in Port Fourchon, US. Photo: courtesy of the US Army, photo by Sgt Michael L. Owens.