Northwestern University is investigating reports that at least three students were sexually assaulted and may also have been drugged at fraternity houses in recent weeks, according to a campus security alert.

In one incident, as many as four female students may have been given a date-rape drug during an event Jan. 21 at the Sigma Alpha Epsilon fraternity house on the Evanston campus, according to a report made to the school Thursday.

Two of those four women believe they were then sexually assaulted, the school said.

The fraternity’s national headquarters — also based in Evanston — released a statement Tuesday saying the fraternity will cooperate with the university investigation, in addition to conducting its own inquiry.

"Any form of assault or sexual misconduct by anyone, brother or not, college man or not, is completely unacceptable, and we do not tolerate actions that are inconsistent with our mission," the statement said. "Sigma Alpha Epsilon always is committed to the safety and well-being of our members and the guest with whom they interact, and that commitment includes making sure our members provide a safe, enjoyable environment in their homes. When incidents are brought to our attention, we take immediate action, and will not hesitate to take corrective actions or impose sanctions on any member or chapter that fails to follow the stringent guidelines we set forth."

The university is also investigating a sexual assault allegation at another fraternity. The attack allegedly took place Thursday and may have involved a date-rape drug as well, according to the security alert.

School officials have not publicly identified the second fraternity.

Northwestern’s Sexual Harassment Prevention Office is investigating the reports.

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