San Francisco 49ers quarterback Alex Smith joins the search for missing California teen Sierra LaMar

(CBS) MORGAN HILL, Calif. - San Francisco 49ers quarterback Alex Smith has joined the search for a missing California girl who was last seen leaving for school over two weeks ago, Fox News reports.

Photos: Calif. teen goes missing on walk to school bus

Nearly 581 volunteers, including Smith, turned out on Saturday to search for 15-year-old Sierra LaMar, who disappeared on March 16 while walking to a school bus stop.

"He (Smith) wasn't there for attention. He was there to search," Marc Klaas, founder of the KlaasKids Foundation, told the newspaper. "It was about his heart. It's certainly a touching thing, and it's a huge thing, too. By showing up, he provided a value that went well beyond his own presence as a searcher."

Last week, searchers found possible items of interest in the case, including condoms and an empty box labeled "handcuffs" not far from where she was last seen.

Santa Clara sheriff deputies confirmed that a volunteer searching for LaMar discovered the items near a dead-end road about two miles from the girl's home.

Law enforcement officials were careful to note that the items were found in an area known to authorities as a place where underage people go to drink alcohol and party.

Investigators said last week that they think LaMar, a sophomore at Sobrato High School, likely was the victim of an acquaintance abduction.

There is currently no named person of interest in the case and police are still treating it as a missing person case.

Anyone with information about Sierra or her whereabouts is asked to contact Santa Clara County Communications at (408) 299-2311. During business hours, tipsters can call sheriff's investigators at (408) 808-4500 or the anonymous tip line at (408) 808-4431.

Complete coverage of Sierra LaMar on Crimesider