Audrey R. Seiler, 20, a sophomore at the University of Wisconsin at Madison, was last seen early Saturday near her off-campus apartment.
It was 2:30 Saturday morning when a security camera recorded Seiler leaving her off-campus residence. She hasn't been seen since, says reporter Bill Hudson of CBS' Minneapolis station WCCO.
A surveillance tape showed her leaving without her coat or purse, and her door was left open, police Officer Jennifer Krueger said Tuesday. She also left her car behind.
Police spokesman Larry Kamholz said there is little information about where Seiler, of Rockford, Minn., was headed.
"We really have nothing to go on," Kamholz told the CBS News Early Show. He added that, "Audrey was an amazing girl one that no one disliked or hated or anything. So it's really hard for us to establish where we're going to go in this process."
Kamholz said Seiler also was walking near her residence when she was attacked on Feb. 1. She was struck from behind by an unknown assailant and knocked unconscious. She was then moved about a block but was not sexually assaulted. Nothing was taken from her.
Police have no evidence linking Seiler's disappearance to the attack, Krueger said.
Seiler's uncle, Scott Charlesworth-Seiler, said 100 friends and family members were assisting in the search.
"We're confident that somebody knows something that will help and we just have to find that person and talk to them, make sure they've seen Audrey's picture and know that she's missing," he said. "So we're hopeful.
Police have been following up on telephone tips while volunteers, many from Seiler's hometown, have searched the area around campus for clues. Fliers were posted at stores, dormitories and apartment buildings.
The university e-mailed 46,000 users of its computer system to appeal for help and established a Web site.
"Some of that has provided us with some information but nothing, nothing really solid I mean just more information about people we need to talk to or go to different places to check out so, nothing that's really a solid lead at this time," Kamholz said.
UW-Madison Provost Peter Spear said the school also offered its counseling services to her family and to students, faculty and staff who know her.
Several other college-age students from Minnesota have disappeared in recent years.
Last November, University of North Dakota student Dru Sjodin of Pequot Lakes, Minn., was allegedly kidnapped from a mall parking lot in Grand Forks, N.D. A Crookston, Minn., man has been charged with kidnapping but no body has been found.
Erika Dalquist, 21, of Brainerd, Minn., was reported missing in October 2002 after she left a Brainerd bar. St. John's University student Josh Guimond, 20, was reported missing in November 2002 after leaving an apartment in Collegeville, Minn.