Two American military helicopters carrying a total of 12 people have crashed off the coast of Djibouti in East Africa. Two crew members have been rescued, but the remaining 10 are still missing. There is no indication that the aircraft were brought down by hostile fire, a US defence spokesman said. The cause of the crash is not yet known. The CH53 marine transport helicopters were based on Camp Lemonier, a French military base in Djibouti. The facility serves as headquarters for a US military operation aimed at stopping militant groups infiltrating the Horn of Africa and the Red Sea. An investigation into the crash is under way.