The five Marines aboard a helicopter that went down in remote, snow-covered woods Tuesday night are dead, a US military spokesperson said Thursday.

The CH-53E helicopter was found near Pine Valley, California, in the Cleveland National Forest. The cause of the crash is under investigation.

The Marines were on a training flight aboard a CH-53E Super Stallion on Tuesday night – flying from Creech Air Force base near Las Vegas to Marine Corps Air Station Miramar in San Diego – but they eventually were “reported overdue,” a Marine Corps unit said Wednesday.

Civil authorities found the helicopter around 9 a.m. PT Wednesday in Pine Valley, a mountainous area some 30 miles east of the San Diego station, the 3rd Marine Aircraft Wing said. The condition of the helicopter was not immediately disclosed.

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 who were aboard the craft are assigned to Heavy Helicopter Squadron 361, Marine Aircraft Group 16, Marines Capt. Stephanie Leguizamon 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.

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.