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.

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 from San Diego.

The helicopter, which was designed to fly in harsh conditions, went missing as a 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, co-pilot, 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 in elevation in the Cuyamaca Mountains, an area which saw as much 8 inches 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, and is also near the Cleveland National Forest, which covers 720 square miles 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 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 range. It was designed to carry up to 55 troops or about 16 tons of cargo both inside and slung outside the cabin.

With an external load, the helicopter can weigh up to nearly 35 tons.

Two CH-53E helicopters were used in the Civil War-torn capital of Mogadishu, Somalia, in January 1990 to rescue American and foreign allies from the U.S. embassy.

The helicopter has been involved in several deadly accidents. In 2018, four Marines from Miramar died when their Super Stallion crashed near El Centro, near the California-Mexico border, during a training mission. The Marine Corps ruled out pilot error for the accident. The victims’ families later sued two companies they alleged provided a defective part that they blamed for the crash.

In 2005, a Super Stallion went down in a sandstorm in Iraq, killing 31 people on board. The accident, blamed on pilot error, was the single deadliest loss of U.S. troops during the war.