By Anne Makovec

Morgan Hill, CA (KPIX/CNN) - The search continues for missing California teenager Sierra LaMar.

The 15-year-old disappeared in March.

The main suspect, who's behind bars, remains silent.

"We really want Sierra back home with us," said Sierra's father, Steve LaMar.

Her family has gathered enough donations to raise the reward from $25,000 to $35,000.

Money to be awarded for information leading to a successful prosecution, or for her safe return.

"We are hoping that this will motivate someone who's been reluctant to come forward," said Steve.

The new flyer includes the word "abducted" instead of "endangered missing," and a picture of the car belonging to the man arrested for her murder, 21-year-old Antolin Garcia-Torres, who has been in jail since May 21, 2012.

Investigators say he's not giving up any information about where Sierra might be.

As volunteers continue to search, dozens of volunteers still show up every week to scour the south Santa Clara County wilderness.

"We still have the same goal that hopefully we are going to find her alive and well and bring her home to her family," said volunteer Janet Locke.

The sheriff's department has searched local reservoirs with high-tech sonar.

They're planning on searching the Chesboro Reservoir within the next couple of weeks as the family hopes someone will eventually come forward.

"If it was their daughter or sister that was missing I'd do that for them. So, we want anyone that knows any information to come forward," said Locke.

Investigators believe Garcia-Torres is the sole suspect in the case.

KPIX/CNN