A human smuggling investigation led to the mass arrest of 16 Marines from the 1st Marine Division yesterday at Camp Pendleton in California. Two other Marines were arrested and charged earlier this month. Some allegedly helped ferry undocumented immigrants into this country in exchange for money.

Camp Pendleton officials say 16 service members were taken into custody on charges ranging from human smuggling to drug-related activities. CBS News

Those 16 Marines are in the brig on the base, and authorities say they've already questioned eight others in alleged drug offenses unrelated to today's arrests.

"It's a shock to the system," said Major Kendra Motz, a spokeswoman for 1st Marine Division.

Thursday's arrests of the Marines occurred in dramatic fashion – in front of their own entire unit.

The Marines were made to line up in morning formation. They were then arrested for offenses that ranged from human smuggling to drug-related activities.

"The release of this information was really so we could be transparent about what happened today," Major Motz said. "It was a very large arrest."

All 16 suspects are members of the oldest active-duty Marine division, headquartered at Camp Pendleton, just 60 miles north of the Mexican border. None of the Marines were among the 6,600 active duty and National Guard troops assigned to bolster border patrol at the southwestern border.

The Marines say Thursday's arrests stemmed from an earlier arrest of two more Camp Pendleton Marines near the Mexican border in early July, reports correspondent Jamie Yuccas.

The pair were pulled over with three undocumented immigrants in their back seat and charged with human smuggling. Both have pleaded not guilty.

The undocumented immigrants said they agreed to pay the Marines $8,000. The Marines said it was not their first time doing this, and Border Patrol expanded the investigation which led to Thursday's arrests.

"If they are in fact found guilty of those crimes, then they'll held appropriately accountable for that," Major Motz said.

In a separate case, on the Fourth of July, an entire platoon of 22 elite Navy SEALs in Iraq allegedly held a drunken party that not only violates regulations against consuming alcohol in Iraq, but there have also been allegations of sexual assault.

When questioned, the whole platoon from SEAL Team 7 in Iraq refused to speak with investigators.

When their commander ordered them home on Wednesday, he said he "lost confidence in the team's ability to accomplish the mission."