SAN DIEGO (AP) — An investigation into troops smuggling immigrants into the United States illegally led to the arrest Thursday of 16 Marines at California’s Camp Pendleton, a base about an hour’s drive from the U.S.-Mexico border.

None of the 16 Marines were involved in helping enforce border security, the Marine Corps said in a news release. They are accused of crimes ranging from human smuggling to drug-related offenses.

Officials could not immediately be reached for additional details.

It comes weeks after two Marines were arrested by a Border Patrol agent on suspicion of smuggling three Mexicans into the United States.

The military said information gained from that operation led to the 16 arrests during a morning battalion formation at Camp Pendleton, the Marine Corps’ largest base on the West Coast that’s about 55 miles from the U.S.-Mexico border.

Eight of the 16 Marines were being questioned about their involvement in drug offenses as part of a separate investigation.

Marines and other U.S. troops were brought in last year to help the Department of Homeland Security reinforce the border by installing razor wire on top of existing barriers. Military troops are barred from making arrests of immigrants.

Officials from 1st Marine Division worked alongside the Naval Criminal Investigative Service in the investigation that started after the July 3 arrests of two Marines charged in federal court with human smuggling.

A U.S. Border Patrol agent stopped Lance Cpl. Byron Darnell Law II and Lance Cpl. David Javier Salazar about 7 miles north of the border after being alerted by other agents that a vehicle similar to theirs was suspected of picking up immigrants in the country illegally, according to the federal complaint.

Three migrants were found in the backseat of a black BMW driven by Law, investigators say. Both Marines are riflemen assigned to 1st Battalion, 5th Marine Regiment, 1st Marine Division, at Camp Pendleton.

Law told the agent that Salazar asked if he was interested in earning $1,000 picking up an "illegal alien." Salazar told authorities that Law introduced him to a man who "recruited" him to smuggle migrants into the country illegally, according to court documents.

The two met on the border the night of July 2 and received instructions from a Mexican cellphone, according to court documents. Law told the agent they picked up a man and dropped him off at a McDonald's in Del Mar, a beach community north of San Diego, but were not paid.

Law said Salazar told him they would be paid if they picked up three immigrants on July 3 near the border, according to court documents.

The three migrants told authorities they were from Mexico and agreed to pay $8,000 to be smuggled into the United States. According to court papers, the migrants were headed to New Jersey and Los Angeles, CNN and ABC News reported.

Marine Corps officials gave no details about how or why the investigation expanded, resulting in the arrest of 16 others.