Over 400 illegal immigrants identified by the Department of Homeland Security have been transported to the United States by an ISIS-linked human smuggling effort, multiple officials reportedly told NBC News. More than 50 of the terrorist-connected illegal immigrants are missing.

Three U.S. officials told NBC News that over 150 illegal immigrants tied to the ISIS network have been arrested, but the whereabouts of at least 50 more are unknown, the New York Post reported.