A mass of Central American teenagers arriving at the U.S. border has fueled the resurgence of the extraordinarily violent MS-13 gang, according to an analysis released Wednesday by a Washington-based think tank.

The Center for Immigration Studies (CIS), which reviewed more than 500 criminal cases, reported that more than one in five gang suspects prosecuted for criminal offenses arrived as so-called unaccompanied minors — at least 120 out of 506.

And the true number likely is much higher, as the think tank was able only to determine whether the defendants entered as unaccompanied minors in 126 of the cases.

Jessica Vaughan, the report’s author, said the actual share of MS-13 gang members who were unaccompanied minors probably is closer to 30 percent. That is the percentage of Immigration and Customs Enforcement (ICE) arrests for which the gang accounts.

MS-13 gang members represent a tiny fraction of the 300,000 Central American youths who have been relocated in the United States since 2012. But Vaughan, the CIS director of policy studies, said there is no doubt the border surge has been a major factor in the growth of the gang.

“There’s no doubt in my mind … It’s not just what we know about where these kids are settling,” she said. “But it’s what we’re finding out about these cases.”

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MS-13, short for Mara Salvatrucha, was founded in Los Angles by Salvadoran immigrants in the 1980s. Members who returned to El Salvador because of deportations brought the gang back home, and then members reintroduced it to the United States — this time far more violent, according to gang researchers.

The report notes that MS-13 gang membership dwindled after President George W. Bush launched an initiative to work with local law enforcement authorities to identify and deport illegal immigrants with gang ties.

Critics, however, complained that federal immigration officials overzealously pursued the cases and swept up people who were not gang members. Former President Barack Obama restricted the policy. Gang arrests by ICE nose-dived from about 4,600 in 2012 to 1,580 last year.

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Vaughan said the gang has stormed back with a vengeance. It is reflected in the criminal cases she reviewed. The cases include 207 murders. At least 48 of the murder defendants came as unaccompanied minors.

The report indicates that more than 100 of the MS-13 defendants were charged with conspiracy and racketeering. Dozens more faced charges that included drug offenses, sex trafficking, attempted murder, sexual assault, and extortion.

Prosecutions took place in 22 states, the report indicates. Those with the highest reported arrests — California, Maryland, New York, and Virginia — also have taken a disproportionate share of the unaccompanied minors.

The report also suggests that policies of non-cooperation with ICE adopted by “sanctuary” jurisdictions may make it harder to disrupt and dismantle MS-13 organizations. Close to half of the MS-13 arrests reviewed by the center — 222 — took place in those jurisdictions.

“They took advantage of catch and release to bring in kids who already were gang members.”

Vaughan said she knows from talking to gang investigators across the country that the MS-13 resurgence is the result of more than aggressive recruiting of unaccompanied minors.

“They took advantage of catch and release to bring in kids who already were gang members,” she said.

That is a reference to U.S. policy toward teenagers who show up at the border. U.S Customs and Border Protection officials can turn Mexican youths around. But that is not the case for unaccompanied teens from any other country. And due to court rulings, U.S. authorities cannot detain minors for longer than 72 hours.

The result is that teenagers get taken — at U.S. taxpayer expense — to the homes of relatives in the United States.

Many of those youths wind up skipping dates at immigration courts and blending into the country like other illegal immigrants.

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“That’s very concerning just in itself,” Vaughan said.

But she added that more troubling is the fact that about two-thirds of unaccompanied minors apply for special green cards under a program for children who have experienced hardship or abandonment by one of their parents. That’s according to a law enforcement roundtable on MS-13 that President Donald Trump convened earlier this month.

Vaughan said MS-13 members who become legal permanent residents become much harder to deport because gang affiliation in and of itself is not grounds to kick lawful residents out of the country.

“I’m worried that a number of these kids [with gang ties] are going to be given green cards,” he said.

PoliZette senior writer Brendan Kirby can be reached at [email protected]. Follow him on Twitter.