NEW YORK (AP) — On Wednesday, masked pro-Palestinian demonstrators clashed with security personnel during a protest held inside Columbia University’s main library.

Social media posts, including videos and photos, revealed numerous protesters pushing through campus security to enter the building. Once inside, they draped Palestinian flags and banners across bookshelves in an elaborately designed reading room. Some protesters seemed to have written “Columbia will burn” over framed images.

Additional footage depicted campus security preventing another set of protesters from gaining access to the library, leading to a standoff where both groups attempted to push one another away.

The university’s president, Claire Shipman, said in a statement Wednesday evening that the protesters who had holed up inside a library reading room were asked repeatedly to show identification and to leave, but they refused. The school then requested the NYPD come in “to assist in securing the building and the safety of our community,” she said.

New York City Mayor Eric Adams subsequently said officers were entering the campus “to remove individuals who are trespassing.”

Following threats by the Trump administration to its federal funding, Columbia in March announced sweeping policy changes.

Among them are a ban on students wearing masks to conceal their identities and a rule that those protesting on campus must present their identification when asked. The school also said it had hired new public safety officers empowered to make arrests on campus.

Columbia University Apartheid Divest, a pro-Palestinian student group, said it had occupied part of Butler Library because it believed the university profited from “imperialist violence.”

“Repression breeds resistance — if Columbia escalates repression, the people will continue to escalate disruptions on this campus,” the group wrote online.