IMPERIAL COUNTY, Calif. (NewsNation) — Five Marines were killed after a military aircraft crashed in California near the southern border, a military official said Thursday.

The aircraft, an MV-22B Osprey, belongs to the 3rd Marine Aircraft Wing. It went down at 12:25 p.m. PT Wednesday near the town of Glamis, which is close to Camp Pendleton.

“We mourn the loss of our Marines in this tragic mishap,” Maj. Gen. Bradford J. Gering, commanding general of the 3rd Marine Aircraft Wing, said in a statement. “Our hearts go out to their families and friends as they cope with this tragedy.”

Identities of the deceased service members will not be released by officials until 24 hours after all next-of-kin notifications are completed, a news release said.

The cousin of one of the Marines, Gage McDonald, however, confirmed to NewsNation that Nathan Carlson, 21, died in the crash.

“Words can’t explain the way I am feeling. We were practically raised together. I am so sorry this happened to you,” McDonald wrote in a Facebook post. “I’m still waiting to get a call from you saying you were just helping and couldn’t get to your phone. I love and miss you Nathan Carlson.”

Carlson’s uncle, Keith McDonald, also told NewsNation local affiliate WTVO that Carlson was one of the Marines on board the Osprey. WTVO reported that Carlson, a 2019 graduate of Harlem High School, was on the swim team.

The news release said equipment recovery efforts have begun and officials are investigating what happened.

Early reports said the aircraft was carrying nuclear material, but the air facility said that was not the case.

The MV-22B Osprey is generally used to transport troops and equipment to support Marine operations. The Osprey can take off and land as a helicopter but transit as a turboprop aircraft.

More than 40 people have died while flying on Ospreys since 1991. Most recently, in March, one crashed in Norway, killing four American service members participating in a NATO exercise.

This is a developing story. Refresh for updates.