Officers began arresting protesters on the University of California Los Angeles campus early Thursday, detaining some with their hands zip-tied behind their backs.

Those who were detained appeared to have been moving willingly with officers, ABC News station KABC reported.

As law enforcement moved into the encampment, some of the protesters began chanting, repeating the phrase "Shame on you" in chorus.

-ABC News' Jenna Harrison and Kevin Shalvey

UCLA officials issued an evacuation order for all protesters in the area of Royce Quad, saying the encampment was "unlawful."

Smoke billowed around law enforcement officials as they began breaking through the barricades on the campus encampment. It was not immediately clear whether the smoke had been dispersed by the police or the protesters.

The encampment in Dickson Plaza, along with all unauthorized tents and structures, had been declared "unlawful," campus public safety officials said in an alert.

"The University requires that everyone must leave the encampment and adjacent areas, as well as all unauthorized structures and tents immediately, until further notice," the alert said.

-ABC News’ Amanda Morris and Kevin Shalvey

California Highway Patrol officers in riot gear streamed early Thursday onto the University of California Los Angeles campus.

The officers were met by a wall of protesters, who appeared unwilling to move. Officials had earlier ordered protesters to abandon their encampment.

Officers were working to tear down barricades of plywood boards that been erected along some of the edges of that encampment.

Los Angeles Police Department officers had earlier retreated from the encampment. At one point, LAPD and protesters briefly scuffled as officers made their way out of the encampment.

-ABC News' Amanda Morris and Kevin Shalvey

At least 90 people were arrested Wednesday during a protest on the campus of Dartmouth University, local police said.

The people who were arrested included both students and non-students, Hanover Police Department said in a statement released Thursday. Charges included criminal trespass and resisting arrest, police said.

Ahead of Wednesday's planned protest, campus security had warned demonstrators that tents or encampments wouldn't be allowed.

"Once tents were erected, Dartmouth Safety & Security made multiple announcements to participants that they must dispel, and they refused," Charles B. Dennis, Hanover's chief of police, said in a media release.

Hanover police and the New Hampshire State Police continued with "multiple" announcements, but some protesters refused to disperse, he said.

-ABC News' Jessica Gorman and Kevin Shalvey

After police and protesters clashed on the campus of the University of Texas at Austin following a dispersal order, leading to some arrests on Monday, the school issued a statement, saying it "took swift action to preserve a safe, conducive learning environment for our 53,000 students as they prepare for final exams."

"UT Austin requested backup assistance from the Texas Department of Public Safety to protect the safety of the campus community and enforce our Institutional Rules, such as the rule that prohibits encampments on campus. Because of the encampments and other violations of the University’s Institutional Rules related to protests, protestors were told repeatedly to disperse. When they refused to disperse, some arrests were made for trespassing. Others were arrested for disorderly conduct," the university's statement read.

UTA said protests since the start of the Israel-Hamas war have happened "largely without incident."

"The University strongly supports the free speech and assembly rights of our community and we want students and others on campus to know that protests on campus are fully permissible, provided that they do not violate Institutional Rules or threaten the safety of our campus community," the statement concluded.

-ABC News' Marilyn Heck