The main entrance to Camp Pendleton, Dec. 21, 2006. One Marine was killed and six were injured on base when their vehicle rolled over during training.
FILE - A sign at the main entrance to California's Camp Pendleton.

PENTAGON - U.S. officials are cracking down on what appears to be a human smuggling operation allegedly involving Marines in Southern California.

Officials, including those with the Naval Criminal Investigative Service (NCIS), arrested 16 Marines early Thursday after they, and hundreds of other Marines, were called to a battalion formation at Camp Pendleton, located roughly 79 kilometers north of San Diego.

According the Marine Corps, the arrests stemmed from a previous human smuggling investigation that resulted in two arrests. 

In that case, Marine Lance Corporal Byron Law II and Marine Lance Corporal David Salazar-Quintero were arrested on July 3 after Border Patrol Agents found them picking up three illegal aliens along Interstate 8, according to a complaint filed with the U.S. District Court for the Southern District of California.

The complaint said the two Marines had been in touch with a recruiter, who offered to pay them for picking up and transporting the illegal immigrants from the interstate to other locations.

Law said he and Salazar-Quintero were never paid for the interaction, according to the complaint.

Marine and NCIS officials said additional information was not being released because the investigations were ongoing. 

"None of the Marines arrested or detained for questioning served in support of the Southwest Border Support mission," the Marine Corps said in a statement. 

Charges have yet to be filed in connection with the latest arrests. 

The Marine Corps said another eight Marines were also taken in for questioning on unrelated drug allegations. 

Thursday's arrests came one day after U.S. Special Operations Command announced a Navy SEAL platoon stationed in Iraq had been sent back to the United States early because of "perceived deterioration of good order and discipline." 

According to media reports, about 20 of the SEALs had been under investigation for drinking or for being aware of the drinking while not on duty. 

Drinking alcohol is forbidden during any combat deployments to the Middle East.