Cornell University has suspended all parties and social events hosted by fraternities after campus police said one student reported a sexual assault and another four reported their drinks being drugged.

The events all allegedly occurred at off-campus houses affiliated with the school's fraternities, according to university officials in a letter to the community on Monday.

The student-led Interfraternity Council, which governs all council-recognized fraternities at Cornell, made the decision to temporarily suspend social events on Sunday following an emergency meeting.

"Fraternity leaders will take this time to implement stronger health and safety plans. No IFC-affiliated social events will resume until student leaders and Cornell staff are confident activities can take place responsibly and safely," wrote Cornell President Martha E. Pollack and Ryan Lombardi, vice president of student and campus life.

The Cornell University Police Department issued crime alerts on Friday alleging at least four students had their drinks roofied at events at off-campus frat houses. Incident happened as early as Sept. 24 and as recently as Nov. 3, according to the alert.

"Students reported to have consumed little to no alcohol at an off-campus location but became incapacitated while attending parties," the police department said. "The individual reported they were exposed to Rohypnol (commonly known as 'roofies')."

On Sunday, a person reported to university police that they were sexually assaulted sometime between 2:30 a.m. and 4:30 a.m. that morning. Police said they were attending an event on the 100 block of Thurston Avenue in Ithaca, the city where Cornell is located. Maps show this area is home to several of the school's fraternities.

According to the Interfraternity Council, Cornell's Greek system is the third-largest in the nation and roughly one-third of the student population takes part in it. There are at least 30 council-recognized fraternities on campus.