Police arrested 25 pro-Palestinian protesters early Tuesday at California State Polytechnic University in Humboldt and ended the occupation of an administration building, university officials said.

Those arrested face a range of charges, including unlawful assembly, vandalism, conspiracy and assault of police officers, the university said in a statement.

"What was occurring was not free expression or a protest," the university said. "It was criminal activity, and there were serious concerns it would spread even further on campus."

The protesters took over Siemens Hall on April 22 and renamed it "Intifada Hall". They fought an early attempt by the police to remove them and later rejected requests from school officials to leave the building. Siemens Hall includes the university president's office, which protesters also occupied.

On Monday night, police at the university, which is known as Cal Poly Humboldt and is more than 275 miles north of San Francisco, began trying to disperse the protesters outside the building.

Media reports said that about 2:30 am, police from various agencies in California moved in and arrested protesters and secured Siemens Hall and a second building, Nelson Hall East, which had been taken over.

Protesters took over Siemens Hall last week and put up dozens of tents on lawns around it. The university then shut down its entire campus.

Pro-Palestinian demonstrators in California have expanded their protest to another college campus, the University of California, Irvine (UCI).

Approximately a dozen tents were set up by midafternoon Monday. The protesters are demanding that UCI divest ties to Israel in response to the Jewish state's military actions following the Oct 7 Hamas attack on Israelis.

"We are demanding diversity from the Western manufacturers. We are also demanding reinvestment into the students, staff and faculty, instead of going to Israel," UCI Diverse Coalition member Sarah told China Daily. "We urge that the school acknowledge genocide of Palestinians and express support for Palestinians, rather than remaining silent on the matter."

Brook Haley, a professor in UCI's humanities department, claimed that Israel's action toward medical professionals in Gaza is part of an effort of ethnic cleansing and genocide.

"And if that's the way Israel decides to treat professionals who are attempting to save people's lives, I'm here to let people know that I disagree with that," he told China Daily.

"And I'm deeply troubled that my tax dollars are contributing to that death, and the university might make money off it, because they invest in companies that are doing business with Israel," Haley added.

A UCI spokesperson emphasized in a statement that the university respects students' rights to engage in free speech and expression, including lawful protest.

On Monday morning, hundreds of students and faculty at the University of California, Los Angeles (UCLA) joined together for a rally in the center of a pro-Palestinian encampment.

UCLA Faculty for Justice in Palestine staged a mass walkout in solidarity with student protesters. The marchers chanted slogans in support of Palestine as they walked on the campus.

Protesters at UCLA are demanding that the university divest from companies doing business with Israel, cut ties with Israeli universities and call for an immediate cease-fire in Gaza.

On Sunday, dueling demonstrations at UCLA led to skirmishes between groups supporting a pro-Palestinian encampment and counter-protesters rallying around the university's Jewish students. Demonstrators breached a barrier established by the university.

School officials said they were "heartbroken" by the violence.

"As an institution of higher education, we stand firmly for the idea that even when we disagree, we must still engage respectfully and recognize one another's humanity," said UCLA spokesperson Mary Osako. "We are dismayed that certain individuals instead chose to jeopardize the physical safety of the community."

Los Angeles Mayor Karen Bass expressed her desire for peaceful expression among protesters at UCLA and USC.

"People have the right to free speech," Bass said in an interview on CNN. "But hate speech, antisemitism, all of that is unacceptable. All students on campus need to feel safe."

Agencies contributed to this story.