Twenty-three people were arrested Saturday at an encampment at Indiana University, the university said.

A group erected tents and canopies on the Bloomington campus' Dunn Meadow Friday night "with the stated intention to occupy the university space indefinitely," in violation of school policy, the university said in a statement.

University and state police gave the group "multiple warnings" midday Saturday to remove the structures before detaining them for charges ranging from criminal trespass to resisting law enforcement, the university said. It is unclear what their affiliation with the university is, the school said.

"The Indiana University Police Department continues to support peaceful protests on campus that follow university policy," the university said in a statement.

The IU Divestment Coalition, a Pro-Palestinian campus group that organized the protest, said many of those arrested were students.

"They are trying to intimidate us, they are trying to break our spirit and our organizing but we will continue to stand for Gaza," the group said on social media.

Ohio State University police have arrested 36 people -- 16 of whom were students -- and charged them with criminal trespassing for encampments that remained overnight.

"Well established university rules prohibit camping and overnight events. On Thursday, April 25, demonstrators, a number of whom were not students, faculty or staff at Ohio State, exercised their First Amendment rights for several hours and were then instructed to disperse," OSU said in a statement.

"Individuals who refused to leave after multiple warnings were arrested and charged with criminal trespass. Arrests are not an action that we take lightly, and we appreciate the support of all of our law enforcement partners to disperse the encampment for the safety of our university community. We have always, and always will, take the action that is in the best interest of our community," OSU said.

Arizona State University announced that campus police have arrested 69 people for trespassing after protesters refused to leave a pro-Palestinian encampment that the university says was "unauthorized."

"Encampments are prohibited on Arizona State University property. Lawful demonstrations can take place except overnight between 11 p.m. and 5 a.m.," ASU said in a statement.

"A group of people – most of whom were not ASU students, faculty or staff – created an encampment and demonstration that continued until 11 p.m. when the group was instructed multiple times to disperse. Individuals who refused to leave after multiple warnings were arrested and charged with criminal trespass," ASU said.

Northeastern University has removed an encampment of pro-Palestinian protesters, with police detaining about 100 people. The university says students who produced valid Northeastern ID were released and will face disciplinary proceedings within the university.

"Earlier this morning the Northeastern University Police Department -- in cooperation with local law enforcement partners - began clearing an unauthorized encampment on the university's Boston campus. What began as a student demonstration two days ago was infiltrated by professional organizers with no affiliation to Northeastern. Last night, the use of virulent antisemitic slurs including "Kill the Jews," crossed the line. We cannot tolerate this kind of hate on our campus," the university said in a statement.

The university added, "As part of clearing the site, approximately 100 individuals were detained by police. Students who produced valid Northeastern ID were released. They will face disciplinary proceedings within the university, not legal action. Those who refused to disclose their affiliation were arrested."

Massachusetts State Police said they responded to Northeastern's request for assistance removing protesters.

"Officers directed protesters to disperse and MSP members assisted in removing protesters who refused to leave. Approximately 102 protesters who refused to comply with orders to disperse were arrested and will be charged by NUPD with trespassing and disorderly conduct. They are being transported to the Suffolk County House of Correction to be booked and processed," MSP said in a statement.

Andrew T. Guzman, the provost and senior vice president for Academic Affairs at the University of Southern California, sent a letter to the school's students, faculty and other members with an update on the situation taking place on campus.

Guzman reiterated the university "values freedom of expression and protects the right of every member of our community to express themselves," but added, "We have well-established policies regarding limits on the time, place, and manner of free expression."

Guzman said the call to shut down the campus stemmed from a confrontation between protesters outside the Doheny Library and security. Security members asked the protesters, many of whom Guzman said weren't affiliated with USC, to leave and remove tents they set up, but the protesters refused, according to the school.

"Their actions have escalated to the point of confrontation and have threatened the safety of our officers and campus community," Guzman said.

Until further notice, only people with "USC identification or verifiable business purpose will be able to access campus, attend classes, and participate in activities" will be allowed on campus, according to Guzman.

"In these challenging times, we call on the Trojan Family to remember that every member of our community is deserving of respect, has the right to be safe on campus, take classes, and participate in other campus activities without fear of harassment or bullying. It should be everyone’s priority to treat each other with kindness and care," he said.

-ABC News' Jenna Harrison