Michelle Le, 26, was last seen May 27 when she told coworkers at a Kaiser Permanente Medical Center in Hayward that she needed to get something out of her car in the garage.
She never returned, but her SUV was found locked a few blocks away.
Police are checking surveillance video for clues about her disappearance.
On Sunday, Le's family expressed frustration with the pace of the Hayward police investigation, and called for the FBI to take over.
A $65,000 reward is being offered for her return.
The Associated Press contributed to this story.