All five Marines who were aboard a military helicopter that went down east of San Diego have been confirmed dead, the U.S. Marine Corps said Thursday.

Their CH-53E Super Stallion helicopter was reported missing Tuesday night during a “routine training flight” from Creech Air Force Base, northwest of Las Vegas to their home base at Miramar Marine Corps Air Station in San Diego..

According to a press release, the helicopter was found Wednesday morning in a mountainous area around 35 miles east of San Diego.

Rough terrain and winter weather complicated the search.

The Weather Channel reported that the area had been under a winter weather warning for elevations 4,000 feet and above. In addition to 6 to 10 inches of snow, gusts up to 60 mph were expected.

President Biden issued a statement expressing how “heartbroken” both he and First Lady Jill Biden were at the loss of the Marines.

“As the Department of Defense continues to assess what occurred, we extend our deepest condolences to their families, their squadron, and the U.S. Marine Corps as we grieve the loss of five of our nation’s finest warriors,” Biden said in a statement. “I am deeply grateful to the San Diego County Sheriff’s Department, the U.S. Air Force Auxiliary-Civil Air Patrol, and other federal, state, and local agencies for their professionalism and dedication in supporting search and recovery efforts.”