At least two others were injured in the crash, which took place on Thursday, according to a tweet from the 1st Expeditionary Marine Force.
Search and rescue efforts are still underway Friday morning with the support of the Navy and Coast Guard.
All service members in the incident are assigned to the 15th Marine Expeditionary Unit, based at Pendleton Field.
“We are deeply saddened by this tragic incident,” said Colonel Christopher Bronzi, the commander of the 15th MEU. “I ask you to keep our marines, sailors and families in your prayers as we continue our search.”
This is a background story and will be updated.