Updated

All seven military personnel aboard a U.S. Air Force HH-60 Pave Hawk helicopter were killed Thursday in a crash in western Iraq near the Syrian border, U.S. defense officials told Fox News.

It's the first deadly aviation crash for the U.S. military in the war against ISIS in Iraq and Syria since American involvement began in 2014. But U.S. Central Command said in a statement the crash "does not appear to be a result of enemy activity."

"This incident is under investigation," the statement said.

The Pave Hawk is a modified version of the Black Hawk helicopter.

"This tragedy reminds us of the risks our men and women face every day in service of our nations," said Brig. Gen. Jonathan P. Braga, director of operations, Combined Joint Task Force-Operation Inherent Resolve. "We are thinking of the loved ones of these service members today."

An accompanying U.S. helicopter immediately reported the crash and a quick reaction force comprised of Iraqi Security Forces and Coalition members secured the scene.

"We are grateful to the Iraqi Security Forces for their immediate assistance in response to this tragic incident," Braga said. "Iraqi Security Forces continue to demonstrate their professionalism, capabilities and flexibility as we continue the fight towards a lasting defeat of [ISIS]."

Names of the fallen will be released by the U.S. Department of Defense after next of kin have been notified.

President Trump tweeted his condolences Friday to the seven people killed in the crash.

"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," Trump wrote.

The incident marked the second aircraft crash for the military in two days.

A U.S. Navy F/A-18F Super Hornet jet crashed off the coast of Key West, Florida, on Wednesday, killing both a pilot and a weapons systems officer.

Fox News' Jennifer Griffin contributed to this report.