"Everybody that knows Audrey is baffled by that," her father, Keith Seiler, told the CBS News Early Show. "Obviously, Audrey had a good reason to leave at that time. We don't happen to know what that reason is at this time."
Seiler, 20, of Rockford, Minn., was last seen leaving her apartment early Saturday on a surveillance tape. Since then, 100 family members and friends have joined a search for her.
"We have such support from family and friends, I think that's what's getting us through right now," her mother Stephanie Seiler told the Early Show.
The search intensified Tuesday, as police searched Audrey Seiler's room and obtained her phone records.
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. Anyone with information about Audrey Seiler's whereabouts is asked to call the Madison police at 1-608-266-6014 or log on to findaudrey.wisc.edu.
"We're still trying to go through the many tips that we're receiving and document those and send officers and detectives out on those tips," said police spokesman Larry Kamholz. "But we have nothing significant at this point."
Adding to the mystery is a Feb. 1 incident in which Seiler 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.
"I don't believe that that has anything to do with it, but we don't know for sure," Stephanie Seiler said of the Feb. 1 attack. "She did talk about it, but Audrey is very independent and straightforward and wanted to get back to school and her life."
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.