SAN DIEGO, CA – Allegations involving 16 U.S. Marines led to their arrest Thursday on human smuggling and drug charges at a base in Southern California, military officials said.

Based on a previous human smuggling investigation, the Marines were arrested at Camp Pendleton, the Marine Corps said in a statement Thursday.

At least eight other Marines are also being questioned about their involvement in alleged drug offenses.

The statement also said that none of the 16 arrested were part of the Southwest Border Support mission, according to a report from NBC.

NBC further reported that two Marines had been arrested July 3 for allegedly helping to smuggle undocumented immigrants across the southern border into San Diego County, allegedly receiving the migrants at a pickup point about 20 miles east of a U.S. port of entry at Tecate and seven miles north of the border.

NBC reported that the drug charges are not related to moving drugs across the southern border, but during the Naval Criminal Investigative Service investigation into the smuggling, investigators found a number of Marines involved with illegal drugs.