People around the campus heard a series of small explosions around 11:30 a.m. on Thursday.
They also saw smoke rising from the roof above the football stadium press box and a small cafe.
"Yeah I mean it might have disrupted their lunch but we were able to mitigate the situation and the incident is under investigation," San Francisco Fire Department Chief Tom Siragusa said.
Nobody was hurt and the damage to the building appears to be minor.
Firefighters also discovered an un-used box of fireworks on the roof. The SFPD sent its bomb squad to the scene to check it out as well.