NEW YORK — New York City police entered Columbia University on Tuesday night to clear out a pro-Palestinian encampment and remove students who had barricaded themselves in a university building, leading to dozens of arrests.

Police in riot gear first entered the campus just after 9:00 p.m. EST after scores of NYPD personnel amassed around the Morningside Heights campus. They were met by protesters chanting on megaphones, "Students, students hold the crowd, NYPD, back down."

At around 9:20 p.m., police surrounded the south lawn of the Gaza encampment but found no students present. Shortly afterward, the NYPD surrounded Hamilton Hall, the college building demonstrators have occupied since early Tuesday morning. The college leadership had ordered the protesters to disperse by 2:00 p.m. on Monday.

Dozens of arrests were made CNN reported, and those arrested were loaded onto buses and taken away. Around 9:35 p.m., a number of students who had formed a picket line outside Hamilton hall were arrested and escorted off the premises as drones were flown around the building. Shortly after, police entered the building via a window and could be seen searching the premises with flashlights. By 10:40 p.m., Hamilton Hall was declared cleared by police, and the NYPD announced around 11 p.m. that the campus has been cleared even as protests continued outside.

Police, upon entering Columbia University, find no one in the south lawn encampment.

Live from Columbia University, Shayeza Walid reports 📹 pic.twitter.com/bm9tAXNJ3w

Columbia University said in a statement that it had been “left with no choice” but to call the police after students blockaded themselves in the building, threatened a staff member and forced out public safety personnel. University President Minouche Shafik requested that the NYPD presence continue on Columbia’s campus through at least May 17, according to a letter sent to the New York Police Department and seen by Al-Monitor. A graduation ceremony is planned for May 15.

Police maintained a massive presence around the university and prevented press, including Al-Monitor, from approaching the school.

A correctional bus is seen leaving Columbia University campus, heading north, @Adam_Lucente reports live 📹 pic.twitter.com/bLBgASdH50

Pro-Palestinian protesters created a Gaza Solidarity Encampment earlier this month, erecting dozens of tents and banners on the campus lawn. Shafik has said the students have the right to protest, but that the encampment is disrupting student life and posing safety concerns, including to Jewish students. Weeks of negotiations between the university and the student protesters failed to yield an agreement.

Early Tuesday morning, protesters occupied the university’s administrative building, Hamilton Hall. In the afternoon, the university said in a statement that students occupying the hall will face “clear consequences,” including possible expulsion.

This is a developing story and will be updated.