SAN DIEGO (AP) — Marine Corps officials say charges are pending against 12 Marines at a California base accused of being involved in smuggling, including driving migrants through a heavily secured US border zone near San Diego once they enter the country illegally.

The Marine Corps said Monday that six other Marines and one sailor detained last month have been released and returned to their command at Camp Pendleton, north of San Diego. All serve in the same unit.

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Those being held include two Marine riflemen who were stopped by U.S. Border Patrol agents on July 3 driving from the US-Mexico border with three Mexicans in the back of a BMW.

That led to the additional arrests. The two Marines pleaded not guilty in federal court.

Officials gave no further details about the others.