Campus police are no longer investigating the rape of a University of Minnesota freshman in her dorm as a stranger sexual assault, authorities said Wednesday evening. The investigation will continue into the report that two men armed with a knife accosted the young woman late at night over the weekend.

The victim reported the assault to U police Sunday, and said she did not know her attackers.

“After further investigation, the University of Minnesota Police Department is no longer investigating the report of a sexual assault in Sanford Hall as a stranger sexual assault,” U spokesman Steve Henneberry wrote in a statement. “As a result of the investigation, UMPD has found no immediate and ongoing threat to public safety related to the case. The U will continue to review any additional information as it becomes available and support the student who filed the report.”

His statement was echoed in a similar one sent Wednesday to all university students and staff by Pamela Wheelock, vice president of university services.

No arrests have been made, Henneberry said Wednesday, and some students who live in that dorm and others are questioning the safety of buildings and the campus as a whole.

While this is the sixth reported sexual assault — including at least three rapes — on or near campus since mid-February, it is unusual because of its location. In the 15 years he has worked at the university, said U spokesman Tim Busse, this is the first armed sexual assault of a student in a dorm that he can recall.

Sexual assaults by strangers are “very rare” in dorm settings, said Katie Eichele, director of the Aurora Center for Advocacy and Education, a crisis intervention group for victims of sexual assault at the U.

When assaults occur within residence halls, it’s almost always by an acquaintance, she said.

The assault occurred between 12:45 and 1:30 a.m. Sunday in Sanford Hall, in the 1100 block of University Avenue SE., according to campus police.

Busse said campus officials are trying to learn how the men got into the building, which has electronic and security personnel measures in place, before they reached the student’s room on the fourth floor.

He acknowledged that students routinely “prop [exterior] doors open and let others tailgate in,” making no dorm building absolutely secure.

He also didn’t rule out that one or more of the men could be students.

Police are reviewing campus video that might help them determine the identity of the suspects, Busse added.

“Unfortunately, we have very limited suspect descriptions at this time,” Busse said, saying only that the student described her attackers as 18 to 21 years old.

The university said in late February that it was raising the bar on the specificity needed before suspect descriptions would be released to the public.

Jenae Herron, 19, also a freshman in Sanford Hall, said, “It’s just kind of frustrating to know that she was just walking in the hallway. … In the place that I’m living, I have to be on guard.”

Herron said it’s easy for people to sneak into dorms, but said she generally feels safe on campus.

She takes advantage of the security monitor program that allows students, staff and visitors to request free security escorts to and from campus locations and nearby neighborhoods.

According to Tuesday’s campus alert:

The student was in the hall outside her room “when she encountered two males who walked her back to her room.”

Once in the room, one of the suspects threatened her with a knife and both of them sexually assaulted her.

Busse said the woman underwent a sexual assault exam at a hospital.

Anyone with information about the assault is asked to call the campus police at 612-624-2677.

No arrests have been announced in any of the other recent incidents. However, there is no indication that this weekend’s attack is related to the earlier assaults, Busse said.

Staff writers Paul Walsh and Nicole Norfleet contributed to this report.