Less than half of the pro-Hamas protesters arrested at New York University last week after refusing to vacate the campus were members of the academic institution, the university said on Wednesday.

Of the 133 protesters arrested on April 22 at Gould Plaza on campus, 65 were students, faculty or other employees of NYU, located in the Greenwich Village neighborhood on the west side of lower Manhattan. It is the largest private university in the United States by enrollment.

“I never thought that as president I would need to rely on the NYPD to secure the safety of our community,” President Linda G. Mills said in the statement.

Mills added that several buildings on campus had to be locked down that evening for security reasons.

At Columbia University in northern Manhattan's Morningside Heights neighborhood, Palestine supporters who were not students or staff were involved in violent protests, according to the city's mayor.

New York City Mayor Eric Adams, speaking on MSNBC’s “Morning Joe” on Wednesday, revealed that “outside agitators,” including one whose husband was convicted for terrorism, played a key role in the anti-Israel and antisemitic protests at Columbia.

"Many people thought that this was just a natural evolution of a protest. It was not. These were professionals that were here," he added.

"I want to send a clear message out that there are people who are harmful and are trying to radicalize our children and we cannot ignore...these outside influences," the mayor stressed.

"I don't know if they're international. I think we need to look into that as well," he said.

Adams said he had urged the school administrators to view the issue from the perspective of student safety and the protection of school facilities, and that after the break-in and vandalism of Hamilton Hall, "I think that the leadership at the school realized that our concern was actually materializing and we had to really move in for the safety of those children and do it in the right way."

Tarik Sheppard, deputy commissioner of public information for the New York City Police Department, said that once they realized outside agitators "would step in" the NYPD started preparing for "worst-case scenarios."

Upon entering Hamilton Hall, the police found heavy industrial chains locked with bike locks on every door. "[T]his is not what students bring to school, okay. This is what professionals bring to campuses and universities," he said.

Manhattan District Attorney Alvin Bragg said on Wednesday it was unclear how many of the 280 arrested at Columbia were outsiders.

NYPD Deputy Commissioner of Intelligence and Counterterrorism Rebecca Weiner said at a news conference on Wednesday alongside Adams, that going through the names of those arrested to determine whether they are affiliated with the universities will "take time."