Police dispatched volunteers to comb the Burlington, Vt., area Wednesday after a three-day investigation into the whereabouts of University of Vermont senior Michelle Gardner-Quinn continued to leave officials baffled by her disappearance.

"Right now the focus is really on trying to find Michelle alive," her sister, Yasmine Rassam, told FOX News Wednesday.

Local police were joined by the FBI and Vermont National Guard as the search reached into the fifth day. About two-dozen volunteers combed the hill section of the city in search of the gray peacoat, green cardigan sweater and black purse that Gardner-Quinn was wearing when she vanished.

On Tuesday, investigators executed search warrants on a home in Richmond, Vt., in connection with the search for missing University of Vermont senior Michelle Gardner-Quinn, officials said Wednesday.

"No one associated with the Richmond address should be considered a suspect in a crime at this time," Burlington Police Chief Thomas Tremblay said at a press conference.

But police had not eliminated the residents of the home, southeast of Burlington, Vt., either.

"We're using these tools [such as search warrants] to help locate potential evidence to eliminate people from suspicion or to help identify persons who may be responsible for the disappearance," Tremblay said.

"Until we're satisfied that we have eliminated folks who had contact with her, we're not going to be done with that avenue of the investigation," he said later.

Tremblay said the investigation remains focused on locating the 21-year-old student and following leads, including finding a 6-foot-tall blond man driving a white Subaru-like hatchback seen around the time of Gardner-Quinn's disappearance, which they continue to call "suspicious."

"Certainly we have indicated this is suspicious ... we don't have a specific crime we can point to now, until we find further evidence," Tremblay said at a press conference Wednesday.

Tremblay told FOX News there was no indication that Gardner-Quinn might be depressed or hiding out on her own.

"By all accounts, all friends and family have indicated that this young lady is a very responsible 21-year-old college student," he said.

Click here to read FOX News correspondent Rick Leventhal's blog from Vermont

Police are seeking a "person of interest," a man they say unsuccessfully tried to lure another woman into his car about 20 minutes before and three-quarters of a mile from where Gardner-Quinn was last seen.

That woman told police the man was about 6-foot, in his 20s, muscular with cropped blond hair, wearing a baseball cap and gray hooded sweatshirt, and reportedly driving a white hatchback, possibly a Subaru, Tremblay said. Police are working on a composite sketch.

"We're not sure of the connection to this incident," Tremblay said.

Friends and fellow students held an evening vigil Tuesday night, organized by the campus women's center and held at a fountain on the college green.

Handmade signs were laid on the brick ledge surrounding the fountain as students, faculty members and friends stood somber and silent, holding candles in front of them. "I Am Scared," read one of the signs. "Somebody saw something. Spread the word. We want Michelle Back," read another.

Gardner-Quinn's parents appeared on television Tuesday to make an impassioned plea for their daughter's safe return.

"I beg of everyone that hears this broadcast, if they know anything at all about where my daughter, Michelle, is today, or where she might have been Friday night, Saturday morning, they tell us instantly," said father John-Charles Quinn.

Gardner-Quinn was last seen early Saturday morning as she headed back to campus after a night of partying with friends downtown.

"We are progressing ... we're following a number of very helpful leads" that have pointed police "in one direction," Tremblay said. "We do not have any specific suspect in mind at this point in time but certainly, helpful leads that are furthering our investigation."

Police interviewed several students who were with Gardner-Quinn when she went out Friday night to celebrate a friend's 21st birthday at several downtown bars. She left the group about 2:15 a.m. to walk back up the hill toward campus, accompanied by a person her friends described as "a random guy," police said.

Police planned to hold a series of informational meetings with the city and campus communities night to discuss the case and public safety concerns. They warned students to travel in groups and to stay in well-lit areas, advising them to walk near the street and away from the shrub-side of the sidewalk.

Police described Gardner-Quinn as 5-foot-8, 135 pounds, with shoulder-length brown hair and a pierced nose. When last seen, she was wearing a gray coat, a green cardigan sweater and a light blue T-shirt, police said.

FOXNews.com's Sara Bonisteel and The Associated Press contributed to this report.