(Adds earlier human-trafficking arrests of two Marines, byline; previous WASHINGTON)
By Steve Gorman
LOS ANGELES, July 25 (Reuters) - Sixteen U.S. Marines were arrested on Thursday at their base in Southern California on suspicion of drug-related offenses and the smuggling of undocumented migrants along the U.S.-Mexico border, U.S. military officials said.
The arrests at Camp Pendleton stemmed from a separate investigation of two other Marines arrested earlier this month on human trafficking charges filed by federal prosecutors in San Diego, a base spokesman said.
Those two Marines, Lance Corporals Byron Darnell Law II and David Javier Salazar-Quintero, were also stationed at Camp Pendleton, about 55 miles (88 km) north of San Diego, according to the spokesman, Marine First Lieutenant Cameron Edinburgh.
"Information gained from the previous investigation gave way to this string of arrests," Edinburgh told Reuters.
The Marine Corps said that in addition to the Marines arrested on Thursday, eight others were detained for questioning on unrelated alleged drug offenses.
The 16 taken into custody were all part of the 1st Marine Division at Camp Pendleton, one of the largest Marine Corps bases in the United States.
None one of those arrested or detained on Thursday was serving in support of the military's mission along the border with Mexico, the Marine Corps said.
Unlike Salazar and Law, the Marines faced prosecution under the military justice system but no formal charges have been brought against them as yet, Edinburgh said.
The precise nature of the alleged wrongdoing was not disclosed, but Edinburgh said the troops were suspected of involvement in the smuggling of undocumented immigrants into the United States from Mexico and various unspecified drug-related offenses.
The two Marines arrested July 3 on charges of transporting aliens for financial gain were arrested by U.S. Border Patrol agents several miles north of the border along a highway in San Diego County.
According to court documents filed in that case, Salazar and Law picked up three undocumented Mexican immigrants by car near the border, guided to a pre-arranged location via cellphone instructions. The three migrants were found riding in the back seat of the Marines' car, and they told investigators they had agreed to pay $8,000 to be smuggled into the United States.
Thursday's arrests came a day after the military said a Navy SEAL team was sent back from Iraq because of discipline issues. An official said it was because, in part, they had been drinking alcohol, something that is prohibited. (Reporting by Steve Gorman in Los Angeles; additional reporting by Idrees Ali in Washington; editing by Cynthia Osterman)