SAN DIEGO — 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.

“To the families of our fallen Marines, we send our deepest condolences and commit to ensuring your support and care during this incredibly difficult time,” Borgshulte said. “Though we understand the inherent risks of military service, any loss of life is always difficult.”

Efforts to recover the remains of the five have begun and an investigation into the crash is underway, according to the statement.

Capt. Stephanie Leguizamon, spokesperson for the wing, said she had little information beyond the statement.

“I do know that it’s cold ... I know that’s been a contentious issue” for searchers in reaching the crash site.

President Joe Biden said in a statement that he and first lady Jill Biden are “heartbroken” to learn of the Marines’ deaths.

“Our service members represent the very best of our nation — and these five Marines were no exception,” Biden said. “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.”

The last known contact with the helicopter was at about 11:30 p.m. Tuesday, Mike Cornette of the California Department of Forestry and Fire Protection told CBS 8 news. That location was based on a “ping” reported to a Cal Fire dispatch center.

The craft was discovered Wednesday morning near the mountain community of Pine Valley, an hour’s drive from San Diego.

Civilian authorities searching on ground and by air located the aircraft, which went down during stormy weather in the Southern California mountains, about 45-miles (72-kilometers) from San Diego.

The helicopter, which was designed to fly in harsh conditions, went missing as an historic storm dumped heavy snow and record rain over California. More rain and snow hit the region Wednesday night, forcing searchers to battle through heavy snow to reach the helicopter.

The five Marines were assigned to Miramar’s Marine Heavy Helicopter Squadron 361, Marine Aircraft Group 16, 3rd Marine Aircraft Wing, the military said in a statement.

While it can carry dozens of people, the normal crew component for the Super Stallion is four: a pilot, copilot, crew chief, and mechanic/gunner, according to a U.S. Navy website.

The military worked with federal, state and local agencies, including the U.S. Forest Service, U.S. Border Patrol, San Diego County Sheriff’s Department and the state Civil Air Patrol.

But weather and rugged terrain made the task difficult. Pine Valley is at about 3,700 feet (1,127 meters) in elevation in the Cuyamaca Mountains, an area which saw as much 8 inches (20 centimeters) of accumulating snow within hours Tuesday night and early Wednesday and saw more falling Wednesday night, according to forecasters.

The area includes San Diego County’s second highest mountain, Cuyamaca Peak, at 6,512 feet (1,985 meters), and is also near the Cleveland National Forest, which covers 720 square miles (1,860 square kilometers) with much of it steep, rocky and with limited trails.

The CH-53E Super Stallion is the largest helicopter in the military and the Marines have used it for heavy-lifting duties around the world for more than three decades. More than 130 are in operation.

Equipped with GPS, infrared radar and other equipment, the aircraft has performed “a full range of military combat operations in Beirut, Somalia, the Persian Gulf, Afghanistan, Iraq and Libya,” according to a U.S. Navy website.

About 99 feet (30 meters) long, the Super Stallion can move troops and equipment from ships to shore, ferry supplies and launch amphibious assaults.

Nicknamed the “hurricane maker” because of the downwash from its three engines, the Super Stallion has a 50-mile (80.5-kilometer) range.