Ann Arbor police were searching for suspects after a University of Michigan student was attacked and sexually assaulted early Sunday morning.
However, on Wednesday, authorities said the assault never happened.
The female student left a fraternity party and got tired of waiting for a ride, so she began to walk home about 2:30 a.m.
She told campus police that four men approached her on Hill Street just off campus, near the East Quad dorms and the Ross School of Business.
The men dragged her into an alley and one of the men sexually assaulted her.
The victim pushed her way free from the assailant and ran to a friend's house and called police.
Female students said the university's department of public safety sent out an immediate alert.
"They send out crime alerts every time something like that happens, so we got a crime alert that it was on Hill Street, near Church," one student said.
Another student said women on campus have stepped up precautions so they will not be crime victims.
"I live in a house with seven girls, so we all walk together or get people to drive and I actually carry a pocket knife with me," that student said.
Ann Arbor police, working with the university's department of public safety, have little to go on. They are asking for anyone with information about the attack to contact them.