The Greek letters will remain on the outside of the building for now, but Northwestern University’s Sigma Alpha Epsilon fraternity has been ordered by its parent organization to stop all social activities, as an investigation into allegations of possible sexual assault at the chapter continues.

“The chapter must halt its operations … not be able to do the normal things a chapter would be able to do — meetings, social events and participating in university events as an organization,” said Brandon Weghorst, a spokesman for the SAE organization, which has its national headquarters in Evanston.

Last week, Northwestern announced on its website that the school had received reports that four women had been drugged at the SAE fraternity house on Jan. 21 — and that another woman had reported being drugged at an unnamed fraternity. Two of the women who were allegedly drugged at SAE also reported being sexually assaulted.

Both the university and SAE are investigating the allegations. Weghorst said members of the Northwestern chapter have been “cooperating, both with us and with Northwestern University officials as part of their investigation.”

Weghorst said some members of the Northwestern chapter have received “threats,” after the university went public with the allegations.

“Obviously the brothers of the chapter are upset,” Weghorst said. “There has been a lot of angst from students who believe the allegations to be true. Some of the members have received threats.”

Weghorst had no specific information about the nature of the threats.

Weghorst said his organization’s investigation — focusing on whether the chapter failed to follow “the strict procedures that we expect our chapters to adhere to” — could last a week or even a month.

The fraternity has about 220 chapters and “colonies” [organizations that are working toward chapter status] across the United States and Canada, Weghorst said.

The kind of cease-and-desist order handed down from headquarters occurs “a few times each year,” Weghorst said.

The order doesn’t require the chapter’s letters to be removed or that students move out of the house, which is privately owned, Weghorst said.