Enforcement Administration’s special agent in charge at the time, those arrested included the highest-level MS-13 leader in the Northeast — presumably Diaz, though he was not publicly identified then.

The 21-count indictment charged the defendants with a variety of crimes, including murder, drug trafficking and conspiracy. All 17 defendants face up to 25 years to life in prison if convicted of the top charges, according to the D.A.’s office.

The arrests followed the grim discovery of the remains of Javier Castillo, 19, of Central Islip, in Cow Meadow Park in Freeport on Oct. 25, and Kerin Pineda, 15, in a wooded area between Freeport and Merrick, just north of the Long Island Rail Road tracks that run parallel to Sunrise Highway, on Oct. 27. The teens’ murders were suspected tobe MS-13-related, but none of the men arrested had been named in connection to them.

Last May, Singas's office joined a DEA investigation of alleged criminal activity of a number of MS-13 “cliques” — subgroups of the gang — in New York, New Jersey, Maryland, Virginia and Texas. The Long Island cliques — said to be operating in Central Islip, Freeport, Glen Cove, Greenport, Hempstead, Roosevelt and Uniondale — are alleged to be under the direct leadership of MS-13 members in El Salvador.

The investigation also turned up several kilograms of heroin allegedly trafficked internationally by gang members on Long Island and elsewhere. Officials said that the street value of the drugs is approximately $1 million. The indictment included a number of counts of cocaine and heroin trafficking in Nassau,