The action by the Rhode Island university -- outlined in a letter signed by two of its vice presidents -- comes as the U.S. Department of Educations investigates
whether dozens of colleges and universities throughout the nation illegally handled sexual violence and harassment complaints.
Brown also announced a review of alcohol policy and social event regulations this spring, according to the letter
"The measures we are taking this spring reflect our interest in preventing sexual assault by addressing the campus climate at Brown," said the letter distributed to the campus. "All Brown community members need to be involved in preventing sexual violence, and all student organizations are expected to ensure that adequate security measures are in place to promote safe events and activities."
Brown said Sigma Chi fraternity has been sanctioned with probation and "suspension of social and university privileges until fall 2016."
"It cannot sponsor social events, has lost access to the chapter room, lounge, library, and basement, and is ineligible to conduct recruitment, rush, or initiation processes," the letter said.
In October 2014, Sigma Chi hosted an unregistered party in the basement of its residence. One student reported "non-consensual contact of a sexual nature that occurred as students were exiting the crowded basement" when public safety officers broke up the party, the letter said. The student was not able to identify the person who touched her.
Phi Kappa Psi was sanctioned with loss of university recognition for four years, including loss of housing, effective immediately.
The fraternity held an unregistered party in October 2014 during which two students reported receiving an "alcoholic drink that contained a date rape drug," according to the letter. The drug was identified as gamma hydroxybutyrate (GHB).
The fraternity was charged with "creating an environment that facilitated inappropriate, potentially dangerous, and possibly criminal behavior by hosting a party where guests were served a drink that contained a date rape drug," the letter said.
One student reported "non-consensual sexual contact that did not happen within the fraternity's facility nor did it involve a member of the fraternity, but its occurrence was a result of the student's incapacitation," said the letter from Russell Carey, executive vice president for planning and policy, and Margaret Klawunn, vice president for campus life and student services.
Brown said no individual member of either fraternity was charged with sexual misconduct.
The fraternities did not immediately respond to calls seeking comment.
A separate federal investigation of dozens of colleges and universities centers on Title IX
, under which a school must ensure that students are not denied or limited in the ability to participate in or benefit from its educational programs or activities on the basis of sex.