NEW YORK (AP) — Dozens of Columbia University students who were arrested for occupying a campus building as part of a pro-Palestinian protest will have their criminal charges dropped, prosecutors said.

At a court hearing Thursday, the Manhattan district attorney’s office said it would not pursue criminal charges for 31 of the 46 people initially arrested on trespassing charges inside the administration building.

Students and their allies seized the building, known as Hamilton Hall, on April 30, barricading themselves inside with furniture and padlocks in a major escalation of campus protests against the Israel-Hamas war.

At the request of university leaders, hundreds of officers with the New York Police Department stormed onto campus the following night, gaining access to the building through a second-story window and making dozens of arrests.

At Thursday’s hearing, prosecutors said they were dismissing charges against most of those arrested inside the building due in part to a lack of evidence tying them to specific acts of property damage and the fact that none of the students had criminal histories.

RELATED COVERAGE Prosecutors try to link alleged bribes of Sen. Bob Menendez to appointment of federal prosecutor Brooklyn preacher who boasted of ties to NYC mayor gets 9 years in prison for multiyear fraud Indian national pleads not guilty in plot to assassinate a Sikh separatist leader in New York City

Stephen Millan, an assistant district attorney, noted that the protesters wore masks and blocked surveillance cameras in the building, making it difficult to “prove that they participated in damaging any Columbia University property or causing harm to anyone.”

All of those students are still facing disciplinary hearings and possible expulsion from the university.

Prosecutors said they would move forward with charges against one person involved in the building occupation, who is also accused of breaking an NYPD camera in a holding cell and burning an Israeli flag during a protest.

Thirteen others arrested in the building were offered deals that would have eventually led to the dismissal of their charges, but they refused them “in a show of solidarity with those facing the most extreme repression,” according to a statement by Columbia University Apartheid Divest, a coalition group representing protesters. Of that group of arrestees, most were alumni, prosecutors said, though two were students.

Nine other defendants who were arrested for occupying another building at City College of New York have also rejected proposed deals with prosecutors, according to the group. Prosecutors said Thursday that they would drop charges against nine others who were involved in the City College occupation.

Inquiries to an attorney representing many of the arrested protesters were not returned.

The building occupations came on the heels of a tent encampment at Columbia University that inspired a wave of similar demonstrations at college campuses across the country.

At Columbia, the group representing protesters have called on the administration cut ties with Israel and to grant amnesty to protesters, vowing that demonstrations would continue to “throughout the summer and beyond.”