The U.S. military says seven U.S. service members were killed when their helicopter crashed in Iraq.
The Pentagon said Friday the crash did not appear to be caused by enemy activity and is under investigation.
Officials say the aircraft, carrying seven people, crashed in Iraq's western Anbar province on Thursday afternoon while on a routine transport mission.
President Donald Trump said on Twitter Friday, "Our thoughts and prayers go out to the families and loved ones of the brave troops lost in the helicopter crash on the Iraq-Syria border yesterday. Their sacrifice in service to our country will never be forgotten."
The Pentagon said another helicopter was flying with the one that went down and immediately reported the crash. Officials say a quick-reaction force, comprised of Iraqi Security Forces and U.S.-led coalition members, secured the scene near the town of Qaim.
"We are grateful to the Iraqi security forces for their immediate assistance in response to this tragic incident," said U.S. Army Brig. Gen. Jonathan Braga, director of operations in the fight against Islamic State in Iraq and Syria.
"This tragedy reminds us of the risks our men and women face every day in service of our nations. We are thinking of the loved ones of these service members today," Braga said.
Military officials have not yet released the identities of those killed.
The United States has been working with Iraqi forces to fight Islamic States militants in Iraq.
In November, Baghdad declared victory over Islamic State, retaking the last Iraqi town held by Islamic States militants -- Rawah, near the border with Syria.
IS militants, however, still carry out attacks in Iraq's north, including one attack earlier this month that left 25 dead.