Honolulu — A multi-agency team scoured the ocean off Hawaii on Wednesday for five soldiers aboard an Army helicopter that went down during a night-time training exercise.The UH-60 Black Hawk went missing when another Army helicopter training with it lost visual and radio contact about 9:30 PM on Tuesday, said Lt. Col. Curtis Kellogg, a spokesperson for the 25th Infantry Division.Two pilots and three crew members were on board, he said. The Army has notified the soldiers' families, Kellogg said."As we do this work, the soldiers and their families are in the forefront of our minds. That's what we're doing this for," Kellogg said.Honolulu Fire Department search and rescue crews found and collected pieces of helicopter fuselage and a helmet in a debris field about 3km off Kaena Point on Oahu.Photos showed Army soldiers unloading suspected debris from the firefighters' boat and personal watercraft at the harbour in the nearby town of Haleiwa.The search later moved to an area about 8km offshore where currents moving in different directions converge.Officials closed the state park at Kaena Point while the search was underway. Kaena is a remote spot northwest of Honolulu where Oahu's northern and western coasts meet to form a small peninsula.The park's sandy coastline is home to a seabird colony and endangered Hawaiian monk seals.A Coast Guard plane, two helicopters and several boats were being used in the search. The Army and Marine Corps joined the effort, as did Honolulu firefighters and lifeguards.Wartime missionTwo Black Hawk crews were conducting training between Kaena Point and Dillingham Airfield when communications were lost, officials said. Clouds and a few showers were in the area at the time.The soldiers were training at night to maintain the skills they need to do their jobs, Kellogg said."Our aviation assets, as well as all of our soldiers, train at night. It's what we do," he said. They need these skills to accomplish their wartime mission, Kellogg said.The two helicopters are elements of the 25th Combat Aviation Brigade based in Hawaii.The UH-60 Black Hawk is a four-bladed, twin-engine utility helicopter manufactured for the Army by Sikorsky Aircraft starting in the 1970s.More than 3 000 Black Hawk aircraft are in service around the world, according to Sikorsky's parent company Lockheed Martin. The US Army owns 2 300 of them.In April, one crew member was killed and two others were injured when an Army Black Hawk helicopter crashed onto a golf course in Maryland during a routine training flight.In 2015, 11 crew members were killed when an Army Black Hawk helicopter crashed into the water off Eglin Air Force Base in Florida.