The nine student agitators arrested after storming an academic building at Barnard College Wednesday night were not students of the elite women’s college, but joined in the melee from nearby Columbia University and Union Theological Seminary, The Post has learned.

A fake bomb threat prompted the evacuation of Barnard College’s Milstein Library, which had been taken over by about 200 protesters, most of them hiding their identities with face masks or keffiyeh headscarves and chanting anti-Israel slogans through bullhorns.

The demonstration echoed a similar campus building takeover at Barnard last week, but this time the group ratcheted up their rhetoric, hanging an Old West-style “wanted” poster of Dean of Students Leslie Grinage and even a shoddy effigy of the school’s president, Laura Rosenbury.

In December, a chilling Instagram post included an illustration of the Barnard campus’ famous statue of Greek goddess Athena lobbing a Molotov cocktail at the Milstein Center — the school’s academic hub and the very same building where the bomb threat was made.

“Barnard first, Columbia next,” the text accompanying the Instagram post read in part.

Columbia University responded to its students being involved in last night’s fracas, promising it was considering its disciplinary options against the students.

“We have been notified that four Columbia students were arrested as part of yesterday’s disruption at Barnard’s Milstein Library and we are working swiftly through our discipline process. We regret that members of our community participated in this unacceptable disruption at Barnard,” a Columbia University spokesperson told The Post.

“Any violations of our Rules, policies, and of the law must have consequences. We remain committed to supporting our Columbia student body of over 36,000 students and our greater campus community during this challenging time.”