Dozens of activists reportedly took over Hamilton Hall and barricaded themselves inside, while university administration and police have yet to comment.
Columbia had begun suspending students who stayed in a two-week encampment and failed to meet a deadline to disperse.
One of the main protest groups, Columbia Students for Justice in Palestine (SJP), posted a message on X calling on everyone to "protect the camp".
The student group announced that they had taken over Hamilton Hall, emphasizing that the building had been the focus of student protests in 1968. Students blocked the doors with wooden tables and chairs.
Another student group said they were taking back the building in memory of 6-year-old Hind Rajab, who was found dead in Gaza earlier this year.
