The service members — five American and two Japanese troops — were injured Wednesday. A total of 17 troops were on board the helicopter at the time of the incident, according to a statement from U.S. Forces Japan.

The helicopter was being flown by soldiers from the 160th Special Operations Aviation Regiment, the Army's elite aviators, officials said.

The H-60 helicopter made the hard landing at 1:46 p.m. local time Wednesday approximately eight miles east of Ukibarujima, or the island of Ukibaru Island, the statement said. The Black Hawk, which was being used for training at the time, was damaged, U.S. Forces Japan said in a statement.

The USNS Red Cloud, a 950-foot medium-speed roll-on/roll-off ship, was underway about 20 miles east of Okinawa at the time, according to the statement.

The injuries sustained by the The seven service members weren't suffered nonlife-threatening injuries, U.S. Forces Japan said. Five of the service members them are American troops; two are members of the Japan Ground Self-Defense Force. 

The injured personnel were taken to the U.S. Naval Hospital at Camp Foster, Japan, according to the military's statement. The helicopter remained on the deck of the USNS Red Cloud, which has a landing pad.

USNS Red Cloud
USNS Red Cloud

The USNS Red Cloud is named for Marine Cpl. Mitchell Red Cloud.

Photo Credit: Navy

At the time, U.S. special operations forces were conducting a maritime training exercise as part of a demonstration of the range of U.S. capabilities to members of the Japan Self-Defense Forces. These types of training events are part of U.S. Pacific Command's military-to-military engagement program, according to U.S. Forces Japan. These exercises are routinely conducted by the U.S. with many nations in the Asia-Pacific region.

The cause of the incident is under investigation. Army officials said all personnel have been accounted for.

The maritime prepositioning ship Red Cloud is nearly 1,000 feet long and displaces 63,000 tons when fully loaded. It's generally crewed by 30 civilians and a ship master. It can hold as many as 1,000 Army vehicles, including 60 Abrams tanks.

The ship is named for Army Cpl. Mitchell Red Cloud, who was posthumously awarded the Medal of Honor for action in Korea, when he single-handedly discovered and engaged a Chinese ambush, alerting his unit to the danger.