The investigation into the disappearance of California teen Sierra LaMar is getting an extra boost with the FBI now getting involved.

Sierra LaMar, 15, was last seen by her mother around 6 a.m. March 16 at her home in Morgan Hill, Calif., about 25 miles southeast of San Jose.

Sierra was not seen at the bus stop, as was her usually routine on a weekday, and never showed up for school the day she went missing.

Sierra sent out a tweet around 6:30 a.m. the day she went missing, replying YES to @Alexialsom's tweet, which said, When I see Her my inner black girl comes out. It's unclear what the discussion was about since @Alexialsom's account no longer exists.

Fox's San Francisco affiliate, KTVU, observed several FBI agents combing through Morgan Hill Thursday.

There were dozens of sheriff's cars in the neighborhood and just before 7 p.m. as officers and FBI agents started going into the backyards of homes, reported.

Authorities said Thursday that they found Sierra Lamar's purse a few miles from her home on Sunday, but found no signs of foul play, according to the San Francisco Chronicle.

Up to 75 police officers have been working the disappearance case, the Associated Press reported, and 150 tips have come in on Sierra Lamar.

Sierra's family is optimistic that she will be found alive and the family has been holding candlelight vigils in honor of Sierra Lamar.

Each day it gets more real, Sierra's mother, Marlene LaMar, said during a vigil Wednesday in Fremont, close to the Lama home, the Associated Press reported. It's been six days and it feels like forever.

Sierra was described as 5-foot-2 and thin with brown eyes and long black hair. Tips on the teen's whereabouts can be called in to the Santa Clara Sheriff's Department at 408-808-4431. Tips are handled anonymously.

A Facebook Page dedicated to Sierra - Help Find Sierra LaMar - Missing From Morgan Hill, California is also a useful resource. The page updates with media reports about Sierra's case.