Officers were dispatched to the 500 block of Turk Street, outside the Federal Building, at about 5:30 a.m. after the briefcase was discovered, according to police.
A bomb squad was called in, and police shut down Turk Street between Hyde and Polk streets, and Larkin between Golden Gate Avenue and Turk Street.
Police have wrapped up the investigation, and streets reopened at about 7:40 a.m.