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

UCLA's public safety department said in an alert Wednesday night that all on campus classes were "required to pivot to remote" through the end of the week.

The announcement comes after overnight protests turned violent, injuring 15 and sending one person to the hospital, university officials previously confirmed.

Campus operations will be limited on Thursday and Friday, the public safety department said in its evening update.

"We have a large law enforcement presence stationed throughout campus to help promote safety," the department said. "Student Affairs will have essential staff on campus to support our students."

Police at UCLA have announced to the gathered crowd that the encampment on campus is an "unlawful gathering."

Demonstrators have been ordered to leave by the LAPD, according to KABC 7.

UCLA is broadcasting a message of its own, telling protesters to disperse. The message, which appears to be recorded, says those who don't leave will be subject to administrative action.

President Joe Biden addressed the nation on Thursday saying that free speech and the rule of law must both be upheld.

"We are not an authoritarian nation where we silence people or squash dissent, the American people are heard. In fact, peaceful protest is the best tradition of how Americans respond to controversial issues," Biden said, speaking from the White House.

But, he condemned the destruction of property, shutting down campuses and forcing the cancelation of classes and graduation, saying it isn't peaceful protest.

"Dissent is essential to democracy, but dissent must never lead to disorder or to denying the rights of others so students can finish the semester and their college education," Biden said.

Biden last commented on college protests on April 22 -- before there was an escalation of suspension and arrests at campuses across the country -- at the time condemning antisemitic actions and those who don't understand the plight of Palestinians in Gaza, a message he reiterated Thursday.

"There is no place for hate speech or violence of any kind whether it's anti-Semitism, islamophobia or discrimination against Arab Americans or Palestinian Americans. It’s simply wrong. There’s no place for racism in America," Biden said.