Dad of missing Indiana University student Lauren Spierer says she called every day

(CBS/AP/WISH) BLOOMINGTON, Ind. - The father of missing Indiana University student Lauren Spierer says he and his wife would typically get a phone call from her every day.

Robert Spierer told the Herald-Times that his daughter was very close to her mother.

He told the newspaper, "She's a compassionate, wonderful, loving person, a good friend to many. She's a great daughter, a great sister. She's just wonderful."

Hundreds of volunteers continued the search for the missing 20-year-old Monday, searching near Spierer's apartment in downtown Bloomington as well as wooded areas, construction sites and nearby lakes.

Spierer was last seen heading back alone to her apartment Friday, walking barefoot after a night out with friends.

Witnesses saw Spierer walking toward her apartment building around 4:30 a.m., reports CBS affiliate WISH. Police say surveillance video shows that the student never arrived at her apartment building after parting with friends.

Police, including canine units, have made several searches of the area where the 20-year-old disappeared, reports WISH.

Over the weekend Spierer's family flew into Bloomington from New York to help search nearby wooded areas, lakes and construction sites. Family tells WISH that the student has a heart condition and requires medication.

The search is set to continue Tuesday.

Spierer is described as a white woman, with longer than shoulder length blonde hair, blue eyes, and a slender build. She is 4-feet-11-inches tall. She was last seen barefoot, wearing a white tank top with a loose light-colored shirt over it, and black full length stretch pants.

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June 6, 2011 - Indiana University student Lauren Spierer missing since Friday