President Donald Trump blamed former President Barack Obama on Twitter for the formation of one of the most notorious gangs.

"The weak illegal immigration policies of the Obama Admin. allowed bad MS 13 gangs to form in cities across U.S. We are removing them fast!" Trump tweeted April 18.

The weak illegal immigration policies of the Obama Admin. allowed bad MS 13 gangs to form in cities across U.S. We are removing them fast! — Donald J. Trump (@realDonaldTrump) April 18, 2017

Trump’s tweet came days after four young men were found brutally murdered in Central Islip in Long Island. The Suffolk County police commissioner said he suspects the MS-13 involvement.

But the president’s post about the Mara Salvatrucha, or MS-13 gang, is misleading.

The gang was established in Los Angeles and spread across the country decades before Obama took office.

Trump’s administration has conducted target operations to arrest criminals, but data is not yet available on how many MS-13 gang members have been arrested or removed.

Ioan Grillo, author of the 2016 book Gangster Warlords: Drug Dollars, Killing Fields, and the New Politics of Latin America, disputed Trump’s conclusion.

"I have seen no evidence that the Obama administration can can be blamed in any way for the existence or activities of the gang in the U.S.," Grillo told PolitiFact.

We asked a Trump spokesman for more information but did not hear back by deadline.

MS-13 history and growth predates Obama policy

Violent gangs, including MS-13, were forming in U.S. cities long before Obama’s presidency.

MS-13 grew out of poor Los Angeles neighborhoods where many refugees from civil wars in El Salvador, Guatemala and Nicaragua lived in the 1980s. (The name Mara Salvatrucha comes from the word "mara" which is a term for gang, "salva" for El Salvador and "trucha," which is slang for clever.)

It later spread to other parts of the United States and in Central American nations.

By the end of the 1990s, the United States government recognized that MS-13 posed a significant criminal threat. Amid an immigration crackdown toward the end of Bill Clinton’s presidency, the government launched an effort to deport foreign-born residents convicted of crimes, including gang members.

In the mid 2000s, U.S. agencies including the FBI and ICE launched initiatives to combat the growth of gangs.

There were several news reports about MS-13’s proliferation in the United States during the 2000s, with interest growing after a 2006 National Geographic documentary on the "World’s Most Dangerous Gang." The documentary showed that by the end of the 1990s, the gang had groups in almost every state.

Attorney General Jeff Sessions discussed MS-13 on the same day as Trump’s tweet, blaming "an open border and years of lax immigration enforcement" for MS-13 recruitment.

Multiple experts said there is no evidence that Obama policies caused the growth of Latino gangs in the United States.

"The big surge was during Bush-Cheney when the drivers of illegal migration in Central America grew, when various crackdowns on crime-filled prisons to bursting point, and when funding for rehabilitation programs declined," said Fulton T. Armstrong, a research fellow at the Center for Latin American and Latino Studies at American University. Armstrong formerly worked as a national intelligence officer for Latin America, chief of staff of the CIA’s crime and narcotics center, and was a career CIA officer.

The growth of MS-13 in the United States is related to draconian domestic policies in the Northern Triangle (Guatemala, Honduras and El Salvador) that have pushed many gang members out of Central America, said Florida International University professor Jose Miguel Cruz.

Héctor Silva Ávalos, a research fellow at American University, said that there has been a new peak in gang activities on the East Coast since 2014 -- especially in Long Island and Montgomery County, Md.

"But this has to do with gang dynamics that have been brewing back in Central America since the Mauricio Funes administration in El Salvador (2009-14) brokered a truce with both MS-13 and Barrio 18," he said. "It is not related to U.S. internal policy."

Elana Zilberg, a University of California San Diego communications professor, said Obama specifically targeted "criminal" aliens (including MS-13 members) in his aggressive deportation program.

"However, Trump’s tweet might be a blunt allusion to Obama’s position on unaccompanied minors from Central America," she said. "That, however, was a policy inherited from the Bush administration."

The number of Central American children coming alone began to increase in fiscal year 2012 and rose significantly in 2014.

The Obama administration in 2014 announced a series of new programs and partnerships with Central American countries to address the issues driving their migration. The Central American Minors program allowed certain parents with lawful presence in the United States to petition for their children in Guatemala, El Salvador and Honduras to come in as refugees. Children ineligible for admission as refugees but at risk of harm could be admitted under parole. The program was expanded in 2016 to allow additional family members to apply.

No data on MS-13 removals under Trump

Trump lauded his administration’s enforcement efforts in a Fox News interview that aired shortly after his tweet.

"We’ve gotten tremendous criminals out of this country," Trump said on Fox & Friends. "I'm talking about illegal immigrants that were here that caused tremendous crime that have murdered people, raped people, horrible things have happened. They are getting the hell out, or they are going to prison."

Trump claimed nothing had been done to remove criminals until he came along. (Here is an overview of some targeted enforcement operations during the Obama administration that led to the arrests of criminals and gang members.)

"It is a serious problem and we never did anything about it, and now we're doing something about it," Trump said.

But ICE data available so far do not prove that Trump is removing MS-13 members "fast" as he tweeted.

In February, the Trump administration said it had conducted targeted operations resulting in the arrest of more than 680 people, including gang members.

At least one of them was a self-admitted MS-13 gang member from El Salvador.

A unit within ICE tracks MS-13 arrests, but monthly data on gang and MS-13 arrests during Trump’s time in office is not available.

From fiscal years 2005 through 2016, immigration officials made 7,051 MS-13 arrests, ICE said.

ICE removal data shows how many individuals were suspected or confirmed gang members. But it does not say to which gang they were affiliated. In fiscal year 2016, ICE removed 240,255 individuals and 2,057 were suspected or confirmed gang members, the agency reported.

During the full two months that Trump has been in office (February and March), a total of 36,467 individuals have been removed, according to an ICE official. ICE said it did not have information on how many of them were gang members.

An executive order signed by Trump expanded removal priorities to include immigrants in the country illegally who have been convicted of crimes as well as those who have been charged with a criminal offense but not yet convicted.

Our ruling

Trump tweeted, "The weak illegal immigration policies of the Obama Admin. allowed bad MS 13 gangs to form in cities across U.S. We are removing them fast!"

MS-13 gangs in the United States were established decades before Obama took office and had been spreading across the U.S. long before his tenure. Experts told us there is no evidence Obama policies spurred their growth. Finally, Obama prioritized the deportation of criminal immigrants.

Immigration officials told us data on how many MS-13 gang members have been arrested and removed under Trump’s administration is not available.

We rate Trump’s claim False.