The search continues for Sierra LaMar, the Northern California teen who mysteriously disappeared on her way to school.

Authorities say there have been no new leads in the case and an analysis of her cell phone, found about a mile from her school bus stop, has yielded no clues, according to a press release issued by the Santa Clara Sheriff's office today.

A search and rescue team found the 15-year-old teen's girl's phone Saturday night alongside the roadway, about a mile away from her home in Morgan Hills, in the opposite direction of her bus stop, said Sgt. Jose Cordoza, sheriff's office public information officer, told ABC News.

The charger for the teen's cell phone was found in her room at home, and the phone looked as if it had been tossed.

Authorities and the Sierra's family were hopeful that the phone could lead them to the girl. But according to the press release, an analysis of the phone yielded no clues, nor did investigators discover anything helpful in her computer.  "Forensic examinations of Sierra's cell phone and computer have not revealed information beneficial to Sierra's disappearance."

"I can't imagine Sierra without her cell phone," Marlene LaMar told ABC News, after her daughter's phone was found. "That's when it became a harsh reality."

Over 150 tips have been called in to authorities  girl, but none have yielded new leads in the case, authorities said.

Cordoza told ABC News that police are regarding La Mar's disappearance as a missing person's case. "There is no information leading us to believe she purposely ran away," he said. " On the other hand we don't have information or evidence associating a crime with her being missing."

Marlene LaMar told ABC News that her daughter's bus driver said the teen never got on the bus the morning of her disappearance.

Sierra's father, Steve LaMar, told ABC News he has no reason to believe she was planning on running away. He said there was "nothing out of the ordinary," about her behavior leading up to her disappearance. He spoke to her Thursday evening and she even asked him to make her a hair appointment for the next weekend- something he says she would never miss.

"I talked to Sierra on the phone Thursday night. She was happy, talking to me about homework. She was asking me to make an appointment so she could dye her hair," LaMar told ABC News.

"She wouldn't miss that appointment -  if you knew my daughter," he said.

Marlene LaMar became worried after her daughter didn't return home from school Friday.

"I was worried when I came home and she wasn't here," Marlene LaMar told ABC News. "That's when my adrenaline, that fear kicked in. That's when a mother has that instinct that something isn't quite right here."

They reached out to the teen's friends, but they grew more concerned when one friend said Sierra wasn't in class earlier that day. They decided to contact authorities around 5 p.m. Friday, after her high school sent them an e-mail saying she didn't show up for school at all that day.

Marlene LaMar told ABC News that her daughter's bus driver said the teen never got on the bus the morning of her disappearance.

Steve LaMar lives in Freemont, Calif., where Sierra LaMar lived until October when she moved with her mother and transferred to Sobrata High School in Morgan Hills.

The couple divorced three years ago.

ABC News has learned that Steve LaMar is a registered sex offender and is currently on probation for committing lewd and lascivious acts with a child under 14 years of age; police stress that Steve LaMar is not a suspect in the investigation.

Police have questioned students at both the teen's current high school and the previous school she attended in Freemont, Cordoza said.

"We have exhausted our search efforts in that area," Cordoza said. "We have investigators talking to kids hoping they can lead us in the right direction as far as where she could be. We are looking for any information, period."

According to the press release, over 100 people have been interviewed so far.

The sheriff's office is broadening their investigation and will be contacting all known sexual offenders within a 10- mile radius of the teen's home. Next they will start to go outside the radius and focus on all registrants in the South County area, authorities said.

Marc Klaas, president of Klaas Kids foundation and an activist for missing children whose daughter Polly was abducted in 1993 and killed, talked to Sierra's mother today and promised his organization will offer help in any way possible.

"I told her to 'keep the hope alive,'" he told ABC News. "Something terrible has happened here and we have to get to the bottom of what that is."

Sierra is 5 foot 2, with long brown hair. She was last seen carrying a pink and black purse.

Her father told ABC News she loves listening to music and was a cheerleader at her previous school. Her mother has said she was always joking and trying to make people smile.

"I just want her back," Marlene LaMar told ABC News. "I love her so much. She always lifted my spirits up. She is very loving. You can feel it when she hugs you and smiles."

Marlene LaMar added, "We are all praying for her to come home and that she is safe."