Four US soldiers are thought to be dead after a military helicopter went down late Wednesday during a routine training flight in the state of Washington, the Army’s Special Operations Command said.

“Our hearts are with the families, friends, and teammates of these Night Stalkers,” Lt. Gen. Jonathan Braga, commander of the US Army Special Operations Command, said Friday in a statement, according to ABC News.

Officials reported that an MH-60 Black Hawk helicopter carrying four people crashed near Joint Base Lewis–McChord at around 9 pm local time Wednesday (0400GMT Thursday).

The command said the four victims were service members assigned to the 160th Special Operations Aviation Regiment.

Authorities said recovery operations are underway, and that the names of the four soldiers will be withheld until the proper time.

The helicopter was on a “routine training flight” when air traffic controllers lost contact with it, a US Army spokesperson said. (Anadolu Agency, excluding headline)