SAN DIEGO (AP) — Five U.S. Marines aboard a helicopter that went down during stormy weather in the mountains outside of San Diego are confirmed dead, the military said Thursday.

Authorities say the CH-53E Super Stallion vanished late Tuesday night while returning to Marine Corps Air Station Miramar in San Diego after training at Creech Air Force Base, northwest of Las Vegas.

“It is with a heavy heart and profound sadness that I share the loss of five outstanding Marines from 3d Marine Aircraft Wing and the “Flying Tigers,” Maj. Gen. Michael J. Borgschulte, commander of 3rd Marine Aircraft Wing, said in a statement.

The names of the Marines were not immediately released.