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. 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.

Efforts are ongoing to recover the five victims’ remains, the Marines said Thursday, and an investigation is underway. 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.”

“We will forever be grateful for their call to duty and selfless service,” Maj. Gen. Michael J. Borgschulte said in a statement. “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.”

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