Cornell University suspended all fraternity parties and social activities after at least four students were allegedly drugged and one was reportedly sexually assaulted.
The incidents apparently occurred over the weekend at off-campus sites that were affiliated with registered fraternities, Cornell said Monday.
Police and the Ivy League school are each investigating the incidents.
"We strongly condemn the actions of all individuals responsible for these criminal violations," the university said. "All found responsible will be held accountable."
Cornell's Interfraternity Council, which governs all fraternities at the school, temporarily suspended fraternity activities voluntarily on Sunday starting immediately.
Fraternity social events will be able to resume once "student leaders and Cornell staff are confident activities can take place responsibly and safely," the school said.