Police made more than 40 arrests as pro-Palestinian protest encampments were dismantled on Friday at the University of Pennsylvania and the Massachusetts Institute of Technology, hours after police tear-gassed demonstrators and took down a similar camp at the University of Arizona.

The dismantling at Penn came around 5:30 am (local time), as campus and Philadelphia police moved in to remove protesters from an encampment that had been in place for more than two weeks.

School officials said protesters were given warnings and the chance to leave without being detained. About 33 people, including students and faculty members, were among those arrested without incident and charged with defiant trespass, the school said.

In Cambridge, Massachusetts, video showed police roaming through the MIT encampment. Police in riot gear arrived around 4 am, encircled the camp and gave protesters about 15 minutes to leave. Ten students who remained were arrested, the university’s president said. A crowd outside the camp began gathering and chanting pro-Palestinian slogans but were dispersed by 6 am.

At the University of Arizona in Tucson, campus police in riot gear fired tear gas late on Thursday at protesters before tearing down an encampment that included wood and plastic barriers on campus. In statement, the university said the encampment violated school policy but did not say whether any protesters had been arrested.

“A structure made from wooden pallets and other debris was erected on campus property after 5 pm in violation of the policy,” the school said in a statement. “University officials issued warnings to remove the encampment and disperse. The warnings were ignored.”

The school also said that police vehicles were spiked, and that rocks and water bottles thrown at officers and university staff.

Tensions have ratcheted up in standoffs with protesters on campuses across the United States and in Europe. Some colleges cracked down immediately, while others have tolerated the demonstrations. Some have begun to lose patience and call in the police over concerns about disruptions to campus life and safety.

The protest movement began three weeks ago at Columbia University. It has since swept college campuses nationwide, with demonstrators generally seeking to draw attention to the deaths from the Israel-Hamas war.