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Over the past six weeks, U.S. Immigration and Customs Enforcement undertook a national operation that has resulted in nearly 1,400 arrests across the country, including 52 locally in D.C., Maryland, and Virginia, according to the agency.

Officials are calling it the largest anti-gang crackdown in ICE’s history, led by the agency’s Homeland Security Investigations unit. Of the 1,378 arrested in this operation nationwide, 933 were U.S. citizens, the agency says.

The D.C. field office, which covers the District and Virginia, made a total of 17 arrests— seven of them were criminal arrests and 10 were arrested for immigration violations (ICE calls these “administrative arrests”). The Baltimore field office, in charge of Maryland, made 35 arrests, which broke down into 14 criminal arrests and 21 administrative arrests.

Of the 52 arrests in the capital region, 29 were MS-13 gang members or associates, according to ICE—16 were arrested by the Baltimore office and 13 by the D.C. office.

The Department of Justice puts MS-13 membership at approximately 6,000 members nationally. As CityLab describes, “One of the peculiarities of MS-13 on the East Coast is its presence in suburbs rather than cities. The gang’s recent killings have taken place in suburban Virginia and Maryland.”

While the greatest activity of ICE’s national operation was in the areas around Houston, New York, Atlanta, and Newark, the agency took time to highlight one aspect of the operation that took place in Falls Church, with an assist from the Fairfax County Police Department. A total of 11 people, all of whom ICE says are MS-13 members, were arrested (10 of them for immigration violations and one criminally arrested) at a “stash house” that law enforcement suspected of being the site of sex trafficking. The arrests occurred on April 26.

Barring a person outright admitting membership, ICE considers an individual part of a gang if he or she meets two or more of the following (at least one of which has to have occurred in the past five years):

1. Subject has tattoos symbolizing or identifying a specific gang
2. Subject frequents an area notorious for gangs and or associates with known gang members
3. Subject has been seen displaying gang signs/symbols
4. Subject has been identified as a gang member by a reliable source
5. Subject has been identified as a gang member though an untested informant
6. Subject has been arrested with other gang members on two or more occasions
7. Subject has been identified as a gang member by jail or prison authorities
8. Subject has been identified as a gang member through seized or otherwise lawfully obtained written or electronic correspondence
9. Subject has been seen wearing gang apparel or been found possessing gang paraphernalia
10. Subject has been identified as a gang member through reasonable suspicion

Associates, according to ICE, are not officially members of gangs but “share the gangs’ values.”

ICE has been busy so far in 2017. Immigration arrests rose by nearly a third during the first weeks of the Trump administration, with the arrests of immigrants with no criminal records more than doubling compared to this time last year, according to The Washington Post.