Investigators will perform a forensic examination of the , the Santa Clara County Sheriff's Office announced.
Sheriff's spokesman Sgt. Jose Cardoza called the development "pretty significant" during a press conference Tuesday afternoon.
He said investigators know who the car's owner is but said there is no person of interest in the case yet. He declined to say where or how the car was found.
On Monday, the sheriff's office released a generic photo of a red four-door Volkswagen Jetta that investigators — who were working off of witness reports and a review of surveillance footage — said was similar to a car possibly associated with the teen's disappearance. They said the vehicle they were seeking had a black hood.
Tuesday afternoon the sheriff's office announced that the car had been found, and its appearance had not been altered.
While meeting with reporters outside the sheriff's office, Cardoza said investigators are maintaining hope for a positive outcome in the case.
"We still do believe she's alive. We don't have any evidence leading us in the direction that she's no longer alive," Cardoza said.
Sierra, 15, left home for school the morning of March 16 and has
not been seen since.
Cardoza said the sheriff's office has determined that the attempted kidnapping of a 16-year-old girl in San Jose the evening of March 23 is not related to Sierra's disappearance.
In that case, a man driving what police described as a red, compact passenger car tried to kidnap the teen using some type of electric device, possibly a stun gun, San Jose police said.
Cardoza said the sheriff's office is still looking into whether two attempted abductions in Walnut Creek in mid-March could be linked to the Sierra LaMar case.
In the Walnut Creek case, a man driving a faded red older-model compact sedan tried twice in two days to lure a 13-year-old girl into his car.
The first time, on the afternoon of March 14, the man approached the Walnut Creek Intermediate School student after she got off of a school bus. He spoke with her and offered her a ride, but she declined.
The next day, the same girl saw the man waiting near the back gate of her school as she was leaving for the day. Police tried to locate the man but he was not found.
The Santa Clara County Sheriff's Office has received 1,600 tips in the Sierra LaMar case as of last week and is seeking additional information from anyone who may have seen the Jetta or had contact with its driver during the month of March.
Anyone with information is asked to contact sheriff's investigators at (408) 808-4500 or call the anonymous tip line at (408) 808-4431.
For previous coverage of the Sierra LaMar case, refer to the Sierra LaMar Disappearance: Comprehensive Updates and Information page.
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—Bay City News