Demonstrations continue to escalate at Columbia University as protesters occupy a building on campus and bar the doors. This comes as the school started suspending students who refused to leave an encampment after a deadline passed.

As of this morning, there is only one way in, or out, of Columbia University's Morningside Heights campus — and only students who live there and essential maintenance staff are allowed through.

The college's public safety team said in an update that the only access point is now at 116th Street and Amsterdam Gate. Barriers have been erected at the usual entrance at 116th and Broadway.

"This access restriction will remain in place until circumstances allow otherwise," the update said.

Earlier, the college urged students to stay away from campus in light of the ongoing protests.

Police were seen removing tents and protesters from an encampment at the University of North Carolina's Chapel Hill from 6 a.m. this morning, according to footage shot by NBC affiliate WRAL of Raleigh.

WRAL reporters saw people with their hands zip-tied being led away and placed in police vehicles. The school said Monday that anyone camping within view of the administration building faced arrest.

The footage showed police officers scuffling with protesters as they dismantled tents and removed tables, air beds and signs.

The UNC-Chapel Hill Students for Justice in Palestine group shared footage on its Instagram account of protesters linking arms to prevent arrests. But it then said after 6.30 a.m. that all members of the "inner encampment" were arrested.

The University of Florida said protesters who broke the rules face being banned from campus for three years suspended from the college, in a message that warned they would not be treated like children.

At least nine were arrested at the University of Florida campus in Gainesville last night, while three were arrested at the University of South Florida campus in Tampa, according to NBC affiliate WPTV of West Palm Beach.

"This is not complicated: The University of Florida is not a daycare, and we do not treat protesters like children — they knew the rules, they broke the rules, and they'll face the consequences." spokesman Steve Orlando said in a statement.

He said the college had "patiently told protesters — many of whom are outside agitators — that they were able to exercise their right to free speech and assembly."

But he added that this did not extend to rule-breaking and that those responsible had ignored warnings.

Protesters at Columbia University have compared their takeover of Hamilton Hall to past movements that saw students occupy the storied building, including the historic 1968 protests against the Vietnam War.

In a statement outlining their demands, demonstrators said the building's takeover represented the "next generation of the 1968, 1985 and 1992 student movements which Columbia once repressed, yet celebrates today."

On its website, Columbia notes how New York City police stormed the campus back in 1968, arresting more than 700 people in an event that "dogged Columbia for years." Today, the "1968 crisis" sits at the top of the school's list of "history and traditions" on its libraries website.

In addition to the 1968 protests against the Vietnam War, demonstrators also referenced demonstrations at the site in 1985, when protesters occupied Hamilton Hall demanding the university divest from companies doing business in South Africa during apartheid and in 1992, when protesters took over the hall rallying against the school's plans to turn the Audubon Ballroom, where Malcolm X was assassinated in 1965, into a biomedical research center.

Despite warnings of suspension for any students involved in the encampment, pro-Palestinian protesters appear to have set up another one in a nearby spot on the main campus.

At least 17 tents were on Lewisohn Lawn, outside Lewisohn Hall, at 3 a.m. this morning. That's a short walk from Hamilton Hall, which protesters have occupied.

A campus building at Princeton University was briefly occupied by pro-Palestinian protesters late last night, before 13 people involved with the incident were arrested, the college said.

Princeton President Chris Eisgruber said the protesters occupied Clio Hall, where the graduate school is based. Of those arrested, five were undergraduates, six were graduate students, one was a postdoctoral researcher and another was not affiliated with the university, he said.

All have been banned from campus and the students could face suspension or expulsion.

A police operation at Tulane University in New Orleans arrested six people late last night, after the college warned students that an encampment would be considered illegal, but a protest encampment there remains in place.

Some students have also been suspended, the university said in a statement early today, while some campus buildings will be shut today and classes held remotely.

The university stressed that "the overwhelming number of these protestors are unaffiliated with Tulane."

TEL AVIV — Israel is waiting for Hamas to provide its response to the current cease-fire proposal before sending its own negotiators to Cairo, an Israeli official told NBC News this morning. 

The official said that in an effort to show flexibility in the talks, Israel had agreed to allow larger numbers of Palestinian civilians to return to northern Gaza than previously countenanced. The question of civilians going back to the north has been a key sticking point in the talks.  

Hamas officials were in Cairo yesterday to discuss the proposal with Egypt. Bassem Naim, a senior Hamas official, tells NBC News that delegation has now left the Egyptian capital.

The U.S. is trying to secure a new truce deal that would see the release of hostages and head off a possible Israeli ground assault on the southern Gaza city of Rafah. Secretary of State Antony Blinken is in the Middle East leading a diplomatic push.