Fifteen-year-old Michael Gritzai went missing just after midnight on New Year's Day.
"Michael left his home in rural Pleasanton. Michael was last seen wearing a maroon hooded windbreaker, black t-shirt, and black 'Dickie' pants," said the sheriff's office in a Twitter post.
According to investigators, the missing teen knows how to use public transportation and often visits downtown Pleasanton.
"Michael's family is very worried about him and is asking for the community's help to locate him. We are all concerned about his safety and are asking for your help to bring him home," said the sheriff's office.
Anyone with information about the teen's whereabouts is asked to contact the Alameda County Sheriff's Office at (510) 667-7721.
RUNAWAY MISSING CHILD pic.twitter.com/1SB6h9Bb6c— Alameda County Sheriff (@ACSOSheriffs) January 2, 2020