Columbia University canceled in-person classes on Monday and new demonstrations broke out on other U.S. college campuses as tensions continue to grow over Israel’s war in Gaza.

Police arrested several dozen protesters at Yale University on Monday morning after officials at the New Haven, Connecticut, school said they defied warnings over the weekend to leave.

And following arrests last week at Columbia, pro-Palestinian demonstrators set up encampments on other campuses around the country, including at the University of Michigan, the Massachusetts Institute of Technology and the University of North Carolina.

The developments came hours before the Monday evening start of the Jewish holiday of Passover.