The University of Southern California's University Park campus has reopened Sunday after a pro-Palestinian tent encampment was cleared out and dismantled, the university said.

All students, faculty and staff must present valid identification, USC said.

New York City Mayor Eric Adams on Sunday defended the police crackdown on college campus protests that have broken out in America's largest city.

"When those protests reach the point of violence, we have to ensure that we use a minimum amount of force to terminate what is perceived to be a threat," " Adams told ABC News "This Week" co-anchor Jonathan Karl.

Adams added that the police intervention resulted from days of communication between the police and school officials.

"We knew we had to get permission unless there's imminent threat to life, or severe threat to property," he said, adding, "We were not going to overstep our legal authority."

When pressed by Karl about criticism, including from some other Democrats, that the response to protesters was disproportionate given that they were largely nonviolent, Adams said, "One has the right to have his or her opinion, and I respect that. ... And I have an obligation and responsibility to ensure the city is safe."

-ABC News' Kristina Abovyan

A pro-Palestinian tent encampment on the University of Southern California campus was cleared out and dismantled Sunday morning without any arrests being made, university officials said.

Joel Curran, a spokesperson for USC, said in a statement that the encampment, established by protesters 12 days ago, was "peacefully" taken down.

“Earlier today, the University of Southern California Department of Public Safety (DPS) successfully removed the illegal encampment rebuilt on the university’s campus. It was necessary to request the Los Angeles Police Department to respond to provide security as this was carried out peacefully," Curran said. "No arrests have been reported. We want to thank LAPD for assisting DPS in clearing the encampment and restoring normalcy for students and community as quickly and safely as possible. We will share more information with our community later today.”

-ABC News' Tristan Maglunog

The University of Southern California said the encampment at University Park Campus has been cleared and the campus remains closed.

In a letter authorizing the NYPD to enter the Columbia University campus and break up the protest, the school detailed the backstory on its recent talks with those in the encampments and the takeover Tuesday night of Hamilton Hall.

According to the letter, from Columbia President Minouche Shafik, an individual "hid in the building" at Hamilton Hall until it was closed and let others in. The group's purpose was "occupying the building," the letter read.

Two security guards were inside the building at the time, and the university said in the letter to the NYPD they were able to "secure their release."

"We believe that while the group who broke into the building includes students, it is led by individuals who are not affiliated with the University," the letter read. "The individuals who have occupied Hamilton Hall have vandalized University property and are trespassing."
Addressing the encampment on the school's Morningside campus, the university told police discussions had been carried out with group representatives, but on Sunday, they "reached an impasse."

At that time, the university says it told the group they did not have permission to "occupy spaces on campus" and were "in violation" of school rules and policies.
On Monday morning, the protesters were told they would be suspended if they didn't disperse by Monday at 2 p.m. ET.

The university said in its Tuesday night NYPD letter that those in the encampment were "suspended" and "not authorized to be on University property and are trespassing."

The university said it believed the actions of those in the protest were escalating. "These activities have become a magnet for protesters outside our gates which creates significant risk to our campus and disrupts the ability of the University to continue normal operations," the letter read.

Columbia's president concluded the letter by asking the NYPD to "help to clear all individuals from Hamilton Hall and all campus encampments."

She further asked police to have a campus presence through May 17 -- graduation is May 15 -- "to maintain order and ensure encampments are not reestablished."

Police moved onto the Columbia University campus a little before 9 p.m. ET and began making arrests.

The NYPD also used a vehicle with an extendable roof ramp to help officers breach Hamilton Hall from an upper floor. From there, the police cleared the building.

The campus encampment and hall were cleared before 11:30 p.m.

-ABC News' Jolie Lash, Aaron Katersky and Joshua Hoyos