Columbia University students were told to shelter in place Tuesday evening due to "heightened activity" on the Morningside campus.

"Shelter in place for your safety due to heightened activity on the Morningside campus," the university’s emergency management operations team said in an alert Tuesday.

Officials warned that "Non-compliance may result in disciplinary action" and that students should "avoid the area until further notice."

The City College of New York said it will hold classes remotely starting on Wednesday until further notice due to "current encampment activities" on the Manhattan campus.

Campus buildings will be closed except to essential personnel, the university said.

The announcement comes nearly a week after the university, which is part of the City University of New York (CUNY) system, said a group of demonstrators calling themselves the "CUNY Gaza Solidarity Encampment" set up a tent encampment on the campus' quad.

"The demonstrators appear to be made up of students, faculty and staff from City College and across the CUNY system and a sizable contingent that is not affiliated with any CUNY campus," City College President Vince Boudreau said in a letter to the community earlier this week, noting that school leaders had begun discussions with representatives from the group.

"We are working to minimize risks to people within the encampment and to protect all members of our campus community, while also minimizing the encampment's impact on campus operations," Boudreau said.

New York City Mayor Eric Adams urged protesters at Columbia University to "walk away" after dozens of demonstrators stormed the campus' Hamilton Hall in what he called a "violent spectacle that serves no purpose."

Adams said the peaceful demonstrations were being co-opted by "professional outside agitators" seeking to "create discord and divisiveness."

"That is why I'm urging every student, every protester to walk away from this situation now. Continue your advocacy through other means," Adams said at a press briefing Tuesday evening. "We will always protect the right to protest, but we must balance that right with the right to keep students in school and our city safe."

"We cannot wait till this situation becomes even more serious. This must end now," he added.

Chief Edward Caban reiterated that protesters who are not Columbia students are working to escalate the situation and said the New York City Police Department is ready to assist the university as needed.

"We have seen the tactics changing in a way that's endangering public safety," he said.

The NYPD showed footage of what Deputy Commissioner for Intel Rebecca Weiner said showed outside actors making barriers inside Hamilton Hall and "escalating" tactics such as scaling buildings and breaking windows. Cameras in the building have also been destroyed, Weiner said.

Individuals who occupied Hamilton Hall could face charges including burglary in the third degree, trespass and criminal mischief, police said.

A Columbia University spokesperson said Tuesday evening that dozens of protesters were in Hamilton Hall.

Some protesters at the University of North Carolina Chapel Hill briefly replaced an American flag with the Palestinian flag on the campus' main quad Tuesday afternoon amid ongoing demonstrations.

The crowd chanted "U.S.A!" and sang "The Star-Spangled Banner" as the American flag was returned to the flagpole, footage shows. The flag was later removed for safekeeping, according to ABC Chapel Hill affiliate WTVD.

The university canceled classes for the rest of the day as of 3 p.m. local time due to the demonstrations on campus.

The University of Minnesota has reached an agreement to end the student-led encampment on campus.

The university will reopen previously closed buildings and the student coalition has pledged not to organize disruptions during final exams and the commencement ceremony.

Representatives of the student coalition will be given the opportunity to address the Board of Regents at its May 10 meeting over its call for a divestment, students will receive amnesty for their encampment, and the university will also explore an affiliation with Palestinian universities, hosting scholars at risk.

"Our meetings have been grounded in listening, learning, and respect, and I believe they were a very positive first step in reaching mutual understanding. Though the original meeting was scheduled for 30 minutes yesterday, we engaged in constructive conversation for more than 90 minutes. We then met two more times to discuss the proposed agreements," University of Minnesota interim President Jeff Ettinger said in a statement.

"We regret that these meetings did not happen sooner, and have committed to regular meetings moving forward to continue to discuss this coalition’s concerns," Ettinger said.

Ettinger also highlighted that the university supports freedom of expression as a fundamental part of its mission.

"While we do not condone tactics that are outside of our policies, we appreciate student leaders’ willingness to engage in dialogue. I value the challenging and healthy conversations we’ve had," Ettinger said.