Over 150 have been arrested, but the whereabouts of over 50 remain unknown, officials said. ICE is looking to arrest them on immigration charges when they are found. The Department of Homeland Security has identified over 400 immigrants who have come to the U.S. from Central Asia and elsewhere as “subjects of concern” because they were brought by an ISIS-affiliated human smuggling network, three U.S. officials tell NBC News. While over 150 of them have been arrested, the whereabouts of over 50 remain unknown, the officials said, and Immigration and Customs Enforcement is looking to arrest them on immigration charges...