The bomb squad was called to the scene around 1:15 p.m. at 360 Ninth Ave., near Geary Boulevard, Sgt. Wilfred Williams said.
Students were not evacuated but limited to a certain area of the campus, away from the package, until they were let out of class, Williams said.
Police also blocked westbound traffic on Geary Boulevard near the school between Seventh and Ninth streets while the investigation was underway.
Around 4:30 p.m., the package with a "suspicious battery substance and other chemicals" inside was deemed safe but police were still investigating where it came from and what the intent was, Williams said.