5 missing Marines confirmed dead following helicopter crash

Five missing Marines have been confirmed dead more than 24 hours after their helicopter crashed in California during a training flight, the U.S. Marine Corps said Thursday.

The Marines had been reported missing when their CH-53E Super Stallion helicopter was "reported overdue" to Marine Corps Air Station Miramar Tuesday night. The helicopter departed from Creech Air Force Base near Las Vegas and was en route to Miramar, in the San Diego area.

The Marines launched a search and asked for help from the San Diego County Sheriff’s Department and Civil Air Patrol.

The sheriff's department said it received a call at 1:50 a.m. PT and sent its own helicopter to search, but the helicopter wasn't able to reach the area due to the atmospheric river storm hitting the region. The sheriff's department said it then sent off-road vehicles to navigate the rough terrain.

The Marines said the helicopter was discovered Wednesday morning at 9:08 a.m. PT.

Efforts are ongoing to recover the five victims’ remains at the crash site, the Marines said Thursday.

"Their fellow Marines have remained by their sides, as Marines do, and took shifts throughout the night at the mishap site -- keeping watch over our fallen despite hazardous weather conditions," Col. James Ford, 3rd Marine Aircraft Wing operations officer, said at a press briefing on Thursday.

Next of kin have been notified, he said.

An investigation is underway to determine the cause of the mishap, Ford said.

President Joe Biden said he is "heartbroken," noting that the training mission was "routine."

"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."

"My prayers are with these brave Marines and their families, loved ones, and teammates," Secretary of Defense Lloyd Austin said in a statement. "As the Marine Corps investigates this deadly crash, it is yet another reminder that across our nation and the world our selfless service members put their lives on the line every day to keep our country safe."

ABC News' Fritz Farrow and Anne Flaherty contributed to this report.