Between classes, when throngs of students stream into and out of Columbia University ’s campus, the security lines can back up like a TSA checkpoint. There’s a switch-back path of metal fencing that leads into a white tent, where two sets of guards check and then swipe campus ID cards before letting students in and out.

Columbia Interim President Katrina Armstrong said Thursday that the agents had search warrants and no one was arrested or detained in the student resident search.