Military officials say the two CH-53 Marine Transport helicopters were conducting a night time training mission Friday over the Gulf of Aden, when they suddenly went down.
U.S. military spokeswoman Major Susan Romano says 12 crew members were aboard at the time of the crash. She says Djibouti soldiers were near the crash site, but were only able to rescue two crew members.
"We don't know the status of the remaining crew members. It's unknown at the time," she said. "We have a task force on the ground, as well as a convoy going out to the crash site to do search and rescue."
Major Ramano says it is unclear what brought the helicopters down. She says an investigation is under way, but that, at this time, there was no indication of hostile fire.
About 1,700 U.S. troops are based in Djibouti as part of a joint task force that conducts training exercises with other militaries in the region.