Dozens of pro-Palestinian demonstrators were taken into police custody on Wednesday evening after occupying part of the main library on Columbia University’s campus in an attempt to rekindle the protest movement that swept the campus last spring.

The protesters, wearing masks and kaffiyehs, had burst through a security gate shortly after 3 p.m. and hung banners in the soaring main room of Butler Library’s second floor, renaming the space “the Basel Al-Araj Popular University,” according to the demonstrators and witnesses at the library.

Columbia security guards blocked them from leaving unless they showed their identification, causing an hourslong standoff. Outside the library, crowds gathered, leading to a chaotic scene. By about 7 p.m., Columbia administrators had called the New York City police back to campus for the first time since the occupation of Hamilton Hall, another campus building, in April 2024.

“Requesting the presence of the N.Y.P.D. is not the outcome we wanted, but it was absolutely necessary to secure the safety of our community,” Claire Shipman, the acting president of the university, wrote in a statement.

Ms. Shipman said that two public safety officers had been injured during a crowd surge outside the library, when some people had tried to force their way in. Several protesters also appeared to have been injured.

The protest comes as the Trump administration has been cracking down on Columbia over what it calls its failure to protect Jewish students from harassment, cutting more than $400 million in federal research funding to the school. The university has been under enormous pressure to stem disruptive pro-Palestinian protests, particularly those that call for an end to the state of Israel.

The tense situation that unfolded around the library over several hours on Wednesday threatened to complicate ongoing negotiations between the Trump administration and Columbia officials seeking the restoration of federal funding.

“While Columbia students try to study for finals, they’re being bombarded with chants for a ‘global intifada,’” Representative Elise Stefanik, a Republican lawmaker pushing for universities to do more to protect Jewish students, posted on social media. “Not a single taxpayer dollar should go to a university that allows chaos, antisemitism, and civil rights violations on its campus.”

The demonstrators had pushed past a library security guard, carrying tote bags and backpacks, before heading up the stairs to the main reading room, video posted on social media showed. After chanting pro-Palestinian slogans for about an hour, some of the protesters tried to leave but were prevented by the row of Columbia public safety officers.

The disruption was limited to a single reading room, a university spokeswoman said. A statement from Columbia said that the protesters would face consequences.

“It is completely unacceptable that some individuals are choosing to disrupt academic activities as our students are studying and preparing for final exams,” the statement said.

Public security officers evacuated students not involved in the disruption from the library, which was filled with people studying. Hundreds of onlookers gathered outside the library.

Just before 5:20 p.m., a group of seven people was released through the back exit of the library on 114th Street. They were free to go, presumably after having their identification checked. A few minutes later, a protester was brought out in handcuffs by the university’s public safety department, which now employs several dozen peace officers who are empowered to make arrests.

The scene became increasingly tumultuous. A building fire alarm began sounding at 5:35 p.m. before going quiet a few minutes later. Some protesters still in the library shouted through megaphones to the crowd outside. There appeared to be at least one injury, with a protester taken out on a stretcher through the back entrance of the library. The person was covered with a white sheet to conceal their identity and had an ice pack held up to their arm.

As 6 p.m. approached, a demonstration in support of the protesters began gathering nearby at Broadway and 114th Street. Police officers assembled metal barricades. The protesters inside the university gates and outside at 114th Street chanted in unison: “No cops, no K.K.K., no fascist U.S.A.”

After Ms. Shipman authorized the police to enter the private campus, events unfolded quickly. At 7:25 p.m., about 30 protesters were escorted out of the building and loaded into police buses by officers in riot gear. The crowd chanted, “Free, free Palestine.” More demonstrators were escorted out, their hands restrained behind them with zip ties.

About 70 demonstrators appeared to have been taken into custody. The police said that they had responded to a trespassing situation at Columbia and that charges were pending.

Columbia has taken many steps to try keep demonstrations under control this academic year, including closing the gates to the main campus to anyone unaffiliated with the university and threatening serious discipline for those who break rules. In part for that reason, the pro-Palestinian movement at Columbia has splintered.

Columbia University Apartheid Divest, the group that organized the occupation of the library, once attracted a wide array of antiwar protesters, but has become smaller and more extreme in its rhetoric. Its leaders, who do not publicize their identities, now publish manifestoes supporting armed resistance by members of groups that United States authorities consider terrorist organizations.

The person for whom demonstrators renamed the library on Wednesday is a Palestinian revolutionary icon who was accused by Israel of planning a large-scale attack and was killed by Israeli forces in 2017. Part of the statement that demonstrators published on Wednesday called on students “to propagate the successes of the heroic Palestinian armed resistance in weakening Israel and U.S. imperialism and inspiring anti-imperialist struggles around the world.”

Anvee Bhutani, Chelsia Rose Marcius, Wesley Parnell and Sharla Steinman contributed reporting.