The investigation involved the Empire Buffet in San Pablo, as well as restaurants in Vallejo and Vacaville, ICE agents said.
Investigators also found undocumented workers living in squalid conditions in three homes owned by restaurant associates in Vallejo, Vacaville and Hercules.
Of those arrested, 20 were taken to detention centers, while one was released for humanitarian reasons, but will appear before an immigration judge.
