(CNN) — Eleven members of the U.S. military were missing after an Army UH-60 Black Hawk crashed into water off the Florida Panhandle during a training mission Tuesday night, representatives of Eglin Air Force Base said.
The helicopter, carrying four crew members and seven Marines, was reported missing during foggy conditions at about 8:30 p.m., and searchers found debris in the Okaloosa Island area near Eglin at about 2 a.m. Wednesday, Eglin spokesman Andy Bourland said.
“We have begun to see debris washing ashore on both the north and the south side of the sound,” Bourland told CNN’s “New Day” on Wednesday morning.
Search and rescue efforts involving the Coast Guard, the Air Force and civilian agencies were underway, Bourland said.
A second Black Hawk on the training mission returned to the base, located about 65 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,” Bourland said.
The cause of the crash wasn’t immediately known. A dense fog advisory was in place for the region, reducing visibility in some areas to less than a quarter-mile.
The seven Marines were assigned to Camp Lejeune, North Carolina. The aircraft were assigned to the Army National Guard in Hammond, Louisiana, the military said.
The names of those aboard weren’t immediately released.
Introduced into Army service in 1979, the UH-60 Black Hawk is the successor to the UH-1 Huey, the iconic military helicopter from the Vietnam War era.
The twin-engine Black Hawk has a maximum speed of 173 mph. Its crew consists of two pilots and two crew chiefs. The Army says a Black Hawk can lift an entire 11-man infantry squad and its equipment.
The service says the Black Hawk’s airframe “is designed to progressively crush on impact to protect the crew and passengers.”
The Black Hawk has been modified for use by other branches of the military. The Navy uses the SH-60, known as the Sea Hawk, the Air Force the MH-60 Pave Hawk and the Coast Guard the HH-60 Jayhawk.