Two British Royal Navy helicopters collided Saturday over the Persian Gulf, killing all seven on board including one American, military officials said.
Pentagon spokesman Maj. Ben Owens said the U.S. officer was among the seven on board who died. The rest were British.
The two Sea King helicopters were not struck by enemy fire, said Group Capt. Al Lockwood, a spokesman for British forces in the Gulf.
"All those on the helicopters have perished," Lockwood said. "It's a great tragedy."
The helicopters crashed about 4:30 a.m., just after taking off from a ship in the gulf, officials said. The cause was under investigation.
"We do have very careful plans and procedures to ensure we have separation of all the aircraft being used," Lockwood said. "Sadly, last night something was not quite right and we are looking to find out what that was as quickly as possible."
The accident is the second involving coalition helicopters since the U.S.-led campaign began.
Eight British Royal Marines and four American Marines died when their CH-46 Sea Knight helicopter crashed before dawn in Kuwait on Friday.
Lt. Col. Ben Curry, a British Royal Marines spokesman, said that crash occurred as troops were being deployed to seize the al-Faw peninsula in southern Iraq.
Manufactured by AgustaWestland in Britain, the Sea King was developed for the Royal Navy and has been in service for more than 25 years.
There are more than 300 in service with both the Royal Air Force and Royal Navy. They are also used by military in Australia, Egypt, Germany, India and Pakistan.