Two were arrested by border agents in Texas. Another was found washing cars at a Santa Ana dealership.

The Salvadoran gang members were responsible, U.S. Immigration and Customs Enforcement officials alleged, for the March assassination of Andrés Ernesto Oliva Tejada, a prosecuting attorney in the homicide unit of the Salvadoran Attorney General’s Office in the southeastern city of Usulután.

Within weeks of the killing, the suspects had made their way to the United States. And experts say this is far from the only case in which the epidemic violence in El Salvador is overflowing into nearly all points north — and especially in Los Angeles, where El Salvador’s two deadliest gangs were founded.

Gang leaders from Mara Salvatrucha, also known as MS-13, and the 18th Street gang have continued to consolidate their power over neighborhoods across Central America, along human smuggling routes and within the narcotics trafficking trade. They’re also increasingly reaching out to affiliated gangs — called cliques — in the United States, according to Special Agent Tony Rodriguez, the section chief for ICE’s National Gang Unit.

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Many cliques already pay dues that help support the gangs in El Salvador, but Rodriguez said leaders have been emboldened by the weakness of the Salvadoran government and their growing power throughout other parts of Central America. Now, he said, MS-13 and 18th Street leaders in El Salvador, “are trying to put pressure on members to get more violent and more active” in the United States.

But there has been some push-back to those demands. “Members here are driven by their own concerns,” Rodriguez said.

As a result, he said, gang leaders in El Salvador have been sending lieutenants to assume leadership positions in the U.S. cliques.

So far, there is no clear connection between the breakdown of a truce between MS-13 and 18th Street in El Salvador and increased fighting between those gangs in the United States — but Rodriguez said that remains a concern.

The Salvadoran gangs — called maras — “are very ruthless,” he said.

“I would say the thing that makes them singularly dangerous more than most other gangs in the United States,” Rodriguez said, “is that they have a lot of command and control based in El Salvador.”

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Because of the connection to gang leaders in El Salvador — and the maras’ violent history — Los Angeles Police Department Officer Eli Villasenor remains wary of an increase in Salvadoran gang activity in Southern California.

Villasenor, who has spent 17 of his 21 years with the department working in street gang interdiction, said history has shown “a war over here in the United States will trickle down to El Salvador … and vice versa.”

Diana Negroponte, author of “Seeking Peace in El Salvador,” about the effort to rebuild the smallest country in Central America following its civil war, believes the rising supremacy of 18th Street and MS-13 in Central America “has already spilled over.”

“It’s spilled over into the maras’ control over human smuggling,” she said.

Negroponte, a public policy scholar at the Woodrow Wilson International Center for Scholars who writes extensively on Central American issues, said maras along human trafficking routes have been increasing their involvement in the piso business — collecting tolls from smugglers passing with migrants throughout the region and inside the United States as well.

“So when we’re looking at this migration element, we’re looking at an industry which has become vulnerable to mara influence,” she said.

Many of the same people and travel routes are used for drug smuggling — and Negroponte said it’s becoming increasingly likely that the Salvadoran gangs will come into greater conflict with established powers in these criminal arenas.

“The interesting question now is whether the maras are now strong enough to confront the Zetas and the Gulf Cartels,” she said, naming two of the most powerful — and violent — narco-trafficking organizations in Mexico, both of which have long histories in Los Angeles.

The LAPD has previously acknowledged the presence of Zetas and Gulf Cartel operatives in the San Fernando Valley, the Westside, and central and South Los Angeles.

The cartels, Negroponte said, “have previously treated the Salvadorans as a nuisance, but that nuisance has now increased its leverage over the past year and a half.”