DURHAM (WTVD) -- The Durham Police Department is investigating a woman's claim she was drugged and sexually assaulted during a fraternity party held by Duke University's Alpha Delta Phi.The frat house party was thrown Jan. 8, which is the same day Duke undergrads returned for spring semester. The rape investigation and university suspension that followed ensures it will be the last party Alpha Delta Phi holds for a while."We had a sexual assault that involved a Duke student," Durham Police Chief Jose Lopez said in a news conference.The alleged assault occurred inside the Alpha Delta Phi fraternity house on the 2500 block of West Chapel Hill Road. It's a private home leased to members of the fraternity. A Duke student says she was drugged and raped inside.Because the crime occurred off-campus, Durham police are leading the investigation. They are "collaborating" with Duke Campus Police."We're hopeful that more folks will come forward, and we'll get more information so we can get to the bottom of it," Chief Lopez said.A knock from ABC11 on the frat house door went unanswered Tuesday afternoon.In court documents, the Duke student says she attended the party with a friend. She said one of the frat members offered to show her his bedroom. She refused and returned to the party.She says she was poured a drink of what she was told was "hot chocolate," saying it didn't smell alcoholic. The next thing she remembers she was waking up the following afternoon in a t-shirt she did not recognize and wearing no underwear.A rape kit was performed at Duke Hospital. Durham police secured a search warrant for the frat house. Investigators found containers with remnants of that "hot chocolate" drink. The question for police -- was it drugged?Police also found bloodstains, along with the women's underwear."At this point, the investigation is ongoing. So, I don't know how many suspects will come out of it," said Lopez."Duke University is cooperating with [Durham Police] in the investigation... Pursuant to Duke's policy, the fraternity has been placed on interim suspension until further notice," said Duke spokesperson Keith Lawrence in a written statement.While the university and police determine what happened, the interim suspension means no recruiting, no events, and no parties for Alpha Delta Phi.