RENO (AP) -- As the search for her enters a fourth week, family and friends are still clinging to hope for the safe return of a 19-year-old college student.

More than 100 volunteers Sunday combed areas around Reno for any sign of Brianna Denison, who police say was abducted January 20 by a serial rapist linked by DNA to a string of attacks near the University of Nevada, Reno campus.

Claudette Springmeyer is a spokeswoman for the volunteer search center based at Circus Circus Hotel and Casino.

She said about 1,700 volunteers have searched a
100-square-mile area around Reno over the last three weeks, and that daily searches will continue until further notice.

Denison, a student at Santa Barbara City College
who was visiting her hometown over winter break, was last seen sleeping on a couch at a friend's off-campus rental house.

Police have said DNA evidence links the suspected kidnapping to two other attacks on women near the university late last year.