Smoke filled the lobby of 850 Bryant St. around 11:15 a.m. No one was injured.
Officers took one person into custody.
Shortly after the smoke cleared the lobby, officers decided not to let anyone enter or leave the building as the SFPD Bomb Squad worked to make sure the scene at Bryant & Sixth St. was safe.
All court proceedings at the Hall of Justice are canceled for the rest of the day. People who were scheduled for afternoon hearings or for jury duty will be rescheduled.
The lockdown has been lifted and the streets are open again.