Sixteen U.S. Marines were arrested Thursday on human smuggling and drug allegations at a base in Southern California, military officials said.

The Marines were arrested at Camp Pendleton based on information gained from a previous human smuggling investigation, the Marine Corps said in a statement Thursday. At least eight other Marines have also been questioned about their involvement in alleged drug offenses.

None of the arrested or detained Marines were a part of the Southwest Border Support mission, according to the military's statement.

Two Marines had been taken into custody July 3 for allegedly helping to smuggle undocumented immigrants across the southern border into San Diego County. The men allegedly received 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, officials said earlier this month.

The drug charges are unrelated to moving drugs across the southern border. During the Naval Criminal Investigative Service investigation into the smuggling, investigators found a number of Marines involved with illegal drugs.

The arrests come hours after United States Special Operations Command separately announced that a Navy SEAL platoon from San Diego would be sent home early from a mission in Iraq "due to a perceived deterioration of good order and discipline." A U.S. defense official told NBC News that the allegations against the Navy SEALs were related to drinking.

Tamara Lawrence, public affairs officer for Naval Special Warfare Command, said in a statement that "the loss of confidence outweighed potential operational risk."

"Leaders at all levels must lead in a way that sustains and sharpens that foundation," Lawrence said. "Discipline is a competitive advantage and enforcing those standards is critical to our success on the battlefield."

The U.S. Marine Corps could not immediately be reached for further information.