The Yale University Police Department has received anonymous reports that two undergraduate students were sexually assaulted at an off-campus party this month, the university said on Friday night.

In a campuswide email alert earlier on Friday, Chief Ronnell A. Higgins said the department had received separate reports — one on Wednesday, the other on Friday — that a student was sexually assaulted by another student on Feb. 8 at the Sigma Phi Epsilon fraternity house one block from campus. The two students knew their alleged attackers, he said.

It was not clear how many assailants may have been involved. The police did not say whether they had identified or spoken with the two students or whether they had any suspects.

There were no signs of activity at the fraternity house on Friday night, and no one answered the door when a reporter knocked.