California (CNN) — Five US Marines have been confirmed dead after their helicopter crashed in a remote area of Southern California during a training flight Tuesday night, according to a news release from their Marine Corps unit.

Efforts are underway to recover their remains, the release said Thursday, after the helicopter – a CH-53E Super Stallion – was reported overdue while en route from Creech Air Force base near Las Vegas to Marine Corps Air Station Miramar in San Diego.

“These pilots and crewmembers were serving a calling greater than self and were proud to do so,” Maj. Gen. Michael J. Borgschulte, commanding general of the 3rd Marine Aircraft Wing, said in a statement Thursday. “We will forever be grateful for their call to duty and selfless service.”

The families of the Marines were notified Wednesday night and early Thursday in person, Col. James Ford of the 3rd Marine Aircraft Wing said during a news conference Thursday. The Marines’ identities are expected to be released 24 hours after the notifications, the unit had said earlier.

‘Being a Marine… was everything’

Those killed were Lance Cpl. Donovan Davis, 21, of Olathe, Kansas; Sgt. Alec Langen, 23, of Chandler, Arizona; Capt. Benjamin Moulton, 27, of Emmett, Idaho; Capt. Jack Casey, 26, of Dover, New Hampshire; and Capt. Miguel Nava, 28, of Traverse City, Michigan; according to a news release from 3rd Marine Aircraft Wing.

The release said the crew was conducting routine flight training.

Langen, 23, was serving as crew chief on the flight, his family said.

“Being a Marine to Alec was everything,” his mother, Caren Langen, told CNN affiliate KNXV Thursday.

Steven Langen, Sgt. Langen’s father, told the station he was a Marine who had flown in a CH-53E Super Stallion, the same type of aircraft that crashed.

“He died with people he wanted to be with, doing the job they wanted to do and loved to do,” said Langen.

Alec Langen was married a month ago, his parents told KNXV.

“We have been confronted with a tragedy that is every service family’s worst fear,” said Lt. Col. Nicholas J. Harvey, their unit’s commanding officer. “Our top priority now is supporting the families of our fallen heroes, and we ask for your respect and understanding as they grieve.”

Recovering remains in ‘hazardous terrain’

Ford said the focus has shifted to recovering the remains of the Marines in what he described as “hazardous terrain,” indicating officials are conducting a ground recovery. He did not elaborate, nor did he take questions from reporters.

“Since our five aircrew of Marine heavy helicopter squadron 361 were located, their fellow Marines have remained by their side, as Marines do, and took shifts throughout the night at the mishap site, keeping watch over the fallen despite the hazardous weather conditions,” Ford said. “Our fellow Marines were, and continue to be, guarded by their brothers and sisters.”

The helicopter was found Wednesday morning in Pine Valley, a mountainous area some 30 miles east of the San Diego station, during a multi-agency search effort that San Diego officials had said was hampered by heavy snow. The crash is under investigation.

The CH-53E is a heavy-lift helicopter that can move troops and equipment and carry as much as 16 tons of cargo, according to the US Navy. The Marines aboard the craft were assigned to Heavy Helicopter Squadron 361, Marine Aircraft Group 16, Marines Capt. Stephanie Leguizamon previously said.

Winds were gusting up to 20 mph Tuesday evening near Pine Valley, and they likely were stronger at higher elevations. Radar indicates a heavy band of precipitation swept through the area between 10 p.m. Tuesday and 4 a.m. Wednesday, with rain at lower elevations and snow at higher elevations.

The aircraft’s last ping was recorded at 11:20 p.m. Tuesday, Cal Fire San Diego spokesperson Mike Cornette told CNN on Wednesday.

President Joe Biden mourned the Marines in a statement Thursday morning, saying he and first lady Jill Biden were “heartbroken” by the news.

“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.

Super Stallion helicopters have been involved in several wrecks over the past decade, at least two of them fatal.

In 2016, 12 Marines were killed when two CH-53E helicopters collided during a night training exercise off Hawaii – a crash military investigators attributed to pilot error. Two years later, four crew members were killed when a Super Stallion crashed during a training mission near El Centro, California.

The outcome of another incident that occurred after a training exercise in Djibouti was considered a “miracle at sea:” 25 Marines and Navy sailors survived when a CH-53E crashed in 2014 as it tried to land on an amphibious transport dock at sea.