Someone contacted the sheriff's office around 2 p.m. to report seeing a man in jail clothing leaving jail grounds.
The sheriff's office has sent deputies to the area to look for the escapee.
Deputies are searching the immediate jail grounds as well as the hills north of the jail in Dublin and San Ramon.
The escaped prisoner has been identified as 57-year old burglary suspect Jose Luis Gonzalez Franco. He was last arrested in Oakland.
Bay City News contributed to this report.
