Dozens of protesters took over a building at Columbia University in New York early Tuesday, barricading entrances and unfurling a Palestinian flag from a window in the latest escalation of demonstrations against the Israel-Hamas war on college campuses nationwide. The school promised they would face expulsion.

The occupation at Columbia — where protesters shrugged off an ultimatum to abandon a tent encampment Monday or be suspended — unfolded as other universities stepped up efforts to clear out encampments. Police swept through some campuses, spurring confrontations with protesters and plenty of arrests. In rarer instances, university officials and protest leaders have struck agreements to restrict the disruption to campus life.