On the surface, it seemed like a simple task: drive to a spot a few miles north of the U.S.-Mexico border, pick up people and then drop them off at a McDonald’s or other spot past San Diego, and make anywhere from $500 US to $1,000 US. No need to cross into Mexico.

In federal court documents, two U.S. marines who were arrested this month for migrant smuggling described such an offer being made to them. Their arrest later led to the stunning arrests of fellow marines at the Camp Pendleton base in California.

The Naval Criminal Investigative Service on Friday said a total of 19 service members have been arrested at the base, including 18 marines and one sailor, a navy corpsman, who all serve in the same unit.

The military personnel are accused of various crimes from migrant smuggling to drug-related offences, but officials have not said exactly how they were involved.

U.S. Border Patrol officials say smuggling rings have been luring U.S. troops, police officers, Border Patrol agents and others to work for them as drivers — a crucial component of moving migrants further into the United States once smugglers get them over the border from Mexico.

Border Patrol agents over the years have routinely caught migrants walking onto Camp Pendleton or floating in skiffs off the coast nearby. The camp, dissected by Interstate 5 leading to Los Angeles, sits along a well-traversed route used by smugglers.

‘Young, gullible and greedy’

Transporting migrants with American drivers can be more effective in avoiding detection. U.S. Customs and Border Protection has broad authority to question and search within about 160 kilometres of the border.

If the driver is in the armed forces, with a military haircut and credentials, that’s a bonus for smugglers because they believe they are more likely to get waved through a checkpoint.

“This is the kind of official corruption that smuggling networks of all kinds, whether it involves people or drugs, really look for,” said David Shirk, an associate political science professor at the University of San Diego.

It’s ideal, he added, for criminal networks to use corrupt officials or military personnel, including “young, gullible and greedy” troops, to help them in their illegal activities.

So-called recruiters for smugglers have chatted up people at casinos and bars, passing out their cellphone numbers and saying if they ever want to make money as a driver, to give them a call, U.S. Border Patrol spokesperson Theron Francisco said. They have also placed ads online.

“They’ve advertised on Craigslist before to get people looking for work by saying drivers needed or people with cars and licences,” Francisco said. “Then they might call or text them and say they can get quick money by going south to an area close to the border and [picking] up people.”

The rings often don’t pay, but keep promising to pay or bump up the money if more trips are done. A driver is not going to go to police to report being stiffed, Francisco said. If a driver gets arrested, smugglers simply move on to find a replacement.

Camp Pendleton Marine Base is the largest Marine Corps’s base on the U.S. West Coast, located about 90 kilometres from the border with Mexico. (Lenny Ignelzi/The Associated Press)

The 19 people arrested at Camp Pendleton have not yet been charged.

They are junior enlisted marines whose monthly salary can run between $2,000 US and $3,000 US a month. None was part of the Trump administration’s efforts that sent troops last year to help reinforce border security.

Marine Lance-Cpl. David Javier Salazar-Quintero told authorities he was recruited by a man he met in a swanky beach community who offered him a way to make extra cash by simply picking up people on the U.S. side of the border and dropping them off north of San Diego.

Salazar-Quintero said a fellow marine, Lance-Cpl. Byron Darnell Law II, introduced him to the man, according to federal court documents, and that he had made such trips for him four times but had not been paid.

One trip was a bust because no one showed up at the pickup spot. He was promised if he did another job he would be paid then and earn even more.

Law told the agent that Salazar-Quintero asked if he was interested in earning $1,000 US by picking up an “illegal alien.”

A U.S. Border Patrol agent stopped Law and Salazar about11 kilometres north of the border on July 3 and found three Mexican migrants who came into the country illegally sitting in the back seat of the black BMW driven by Law, according to the federal complaint.

The three migrants told authorities they agreed to pay $8,000 US to be smuggled into the United States and were headed to Los Angeles and New Jersey, according to court documents.

Both marines are riflemen at Camp Pendleton. They have pleaded not guilty to smuggling charges in federal court.

U.S. Marine Corps officials said information from that case helped them identify the other people they arrested.

In a dramatic move aimed at sending a message, authorities made the arrests at Camp Pendleton as the marines and navy corpsman gathered in a battalion formation Thursday. Camp Pendleton is the largest U.S. Marine Corps’s base on the U.S. West Coast, about 90 kilometres from San Diego’s border with Mexico.