At its headquarters, the TSC operates a 24-hour command center, resembling something from a Hollywood thriller, complete with giant wall-screen projections and signs flashing “SECRET.”

Officials said that when a law enforcement or homeland security officer in the field stops a person whose name matches a name in the TSC’s databases, the officer is supposed to phone the TSC command center for instructions. Based on information in the databases, the TSC then will advise the officer in the field how to proceed, which could range from releasing the suspect to calling in federal officers as backup.

The command center gets between 100 and 150 inquiries a day, of which an average of 55 involve individuals who turn out to be listed on one of the federal watch lists, officials said. Of those calls, about 60 percent come from federal officers at border or airport security posts; the rest come from local police.