A U.S. Marine was behind bars Tuesday for allegedly smuggling undocumented immigrants into the United States.
Meanwhile, six of the 23 Camp Pendleton Marines arrested and charged this summer for alleged human smuggling have pleaded guilty, military officials announced Tuesday.
The announcement came one day after a junior-enlisted Marine from the 1st Marine Division was arrested by border patrol officials for allegedly transporting undocumented immigrants at the San Ysidro Port of Entry.
The unidentified Marine — who was arrested at around 1:30 a.m. Monday — is being held in civilian custody, according to USMC officials, and may face charges in either civilian or military court.
U.S. Customs and Border Protection and the Naval Criminal Investigative Service were investigating the alleged crime, Marine Corps public affairs 1st Lt. Cameron Edinburgh said.
"We will continue to cooperate with civilian authorities on this case going forward," the spokesman said.
No further information about the allegations was immediately available, including the suspect's identity, which was being withheld "out of respect for their privacy," according to Edinburgh.
RELATED: 16 Camp Pendleton Marines Arrested In Migrant Smuggling Investigation
In July, military police arrested 23 Camp Pendleton-based Marines on suspicion of human trafficking, as well as drug and weapons offenses.
Six have entered guilty pleas at courts-martial, another 13 have agreed to be discharged from the Marine Corps in exchange for dismissal of charges in the military system, and four remain in pretrial court-martial status.
The service members from the 1st Marine Division were detained during three separate incidents this July — including a widely publicized mass arrest during a battalion formation at Camp Pendleton — stemming from allegations of human trafficking, drug distribution and weapons charges.
A court date for the four awaiting trial has not yet been set, Edinburgh said.
It was unclear what kind of sentence the six who pleaded guilty will face.