All immigrants who cross the border illegally will be charged with a crime under a new “zero tolerance” border enforcement policy, Atty. Gen. Jeff Sessions said Monday, launching a crackdown that could overwhelm already-clogged detention facilities and immigration courts with hundreds of thousands of new cases.

Sessions also said that families who illegally cross the border may be separated after their arrest, with children sent to juvenile shelters while their parents are sent to adult detention facilities. Until now, border agents tried to keep parents and their children at the same detention site.