At least two students have been treated for consuming the “date-rape drug” Rohypnol after attending off-campus parties in the past two weeks, according to warnings sent to House e-mail lists yesterday.

The e-mail, which was first sent by the Office of Sexual Assault Prevention and Response to Sexual Assault (OSAPR) and Sexual Harassment (SASH) tutors, said the Office knows of two students who sought medical treatment after becoming sick at parties and received toxicology test results indicating the presence of Rohypnol or a related drug in their blood streams.

Although these drugs are sometimes used as “date-rape drugs” because they have the ability to induce unconsciousness and temporary amnesia, the e-mail said the two cases are not known to have resulted in sexual assaults.

One of the students was treated for Rohypnol poisoning after attending a punch event for a female final club held in a Boston night club last week. The circumstances surrounding the other case are unknown.

The e-mail to SASH tutors did not say where the two students sought treatment.

David S. Rosenthal, director of University Health Services (UHS), said of the most recent admissions for alcohol-related illness, none have exhibited obvious signs of Rohypnol poisoning.

“I talk with Harvard students every week who think/believe they have been drugged, but very few ever seek medical attention and even fewer actually get tested for these substances,” OSAPR Director Susan B. Marine wrote in an e-mail. “I am thankful that these students and their friends took the situation seriously, sought medical help, and were tested. This is the only way we have to know for sure if these substances are being used, intentionally or otherwise, at social events attended by Harvard students.”

In addition to these two confirmed cases, Pi Kappa Alpha (Pike) President Joe H. Mujalli ’04 said a Pike member left the fraternity’s Pi Ki Ki party last Thursday night feeling “unexplainably” sick, but did not go to the hospital.

Mujalli said the incident highlights the responsibility of groups that host open parties to be careful of what people drink.

The Office’s e-mail warns students not to consume unknown substances, accept drinks from people they don’t know or leave drinks unattended.

“I imagine that there are a number of students who already do a lot of those things,” said Sharrona Hyla Pearl, a SASH tutor in Kirkland House who sent the e-mail advisory to her House list. “I really hope that people are very careful about what they drink.”

The e-mail describes the drugs as “colorless and odorless” and encourages students who experience “nausea and vomiting, unconsciousness, dizziness, shallow or irregular breathing or heartbeat, decreased blood pressure, drowsiness, visual disturbances, confusion, gastrointestinal disturbances and/or urinary retention” to seek medical attention immediately.

Rosenthal would not provide UHS statistics on Rohypnol poisoning at Harvard.

Because of the blood stream’s short retention of such drugs, it is difficult to compile accurate statistics on the number of cases, according to Marine. The e-mail said over 5,000 cases of Rohypnol-related sexual assault have been reported so far in the U.S. in 2003.

Rohypnol and similar sedatives, known as “roofies,” are generally not traceable in the blood stream 12 hours after consumption.