University of Minnesota fraternity members are being threatened by a former Marine who claims his daughter was sexually assaulted at an unnamed fraternity event, according to a Thursday email from the Interfraternity Council’s president to chapter leaders.

Fraternities were first warned about threats of physical harm directed at members in an anonymous letter sent to the University’s Interfraternity Council Tuesday. In Thursday’s update to chapter leaders, IFC President Simon Beck said the letter-writer threatened to “kidnap and mutilate two members of every fraternity” until the person who allegedly sexually assaulted his daughter comes forward.

While Beck said the threat could be a hoax, he asked the University’s fraternity community to take safety precautions.

“The safety of our members and our community remains our top priority,” he said in the emailed letter. “It is crucial to take this threat seriously and assume the author has the full intent and capability to act on these threats.”

Fraternity members have been asked to not wear anything with chapter letters and to not walk alone at night, according to Beck’s Tuesday email.

Fraternities were also encouraged to lock doors and windows to chapter facilities, call the school’s security escort service while walking at night and use the Gopher Chauffeur for rides, according to an email sent to chapter presidents Wednesday by Vice Provost for Student Affairs and Dean of Students Danita Brown Young and University of Minnesota Police Department Chief Matt Clark.

The University of Minnesota Police Department is investigating the incident, according to the email. The Minneapolis Police Department is also involved in the investigation, according to UMPD.

“We are aware of a recent, anonymous threat that was mailed to the Interfraternity Council targeting fraternities and their members,” Brown Young and Clark said in the email. “The safety and security of our students is our top priority, and we take this issue very seriously … and we are working in close coordination to address this situation.”

A meeting was held Wednesday night with chapter leaders, Beck said Thursday. He said the importance of the safety protocols put in place was stressed at the meeting.

A Friday event is planned for people affected by the threat, Beck said. A UMPD offer and staff from University Counseling Services will be there as resources.