The caller spoke to a police dispatcher at 10:05 a.m., at about the same time that a moderate earthquake shook up Palo Alto. The caller warned that the bomb would go off in about hour. It did not.
Police Lt. Sandra Brown said workers were asked to leave the building at about 10:40 a.m. as a precautionary measure. Bomb-sniffing dogs from Stanford, San Jose and Sunnyvale were called in to search the eight-story structure and the three garage levels. As of 12:30 p.m., no bombs were located.
A section of Bryant Street between Hamilton and Forest avenues was closed to traffic while City Hall was searched.
"We took the highest precautions," Brown said. "Why take any chances?"
About 350 city employees were asked to take an early lunch. Dozens of them congregated next to the Downtown Library, across the street from City Hall.
"We'd much rather be inside, working," City Clerk Donna Grider said.
At about 12:30 p.m., after about two hours of inspection, City Hall employees were informed that they can return to the building in about an hour.
The bomb threat also interrupted the meeting of the city's Architectural Review Board. The board was concluding a public hearing on streetscape improvements on El Camino Real when Amy French, current planning manager, informed board members that they may soon have to evacuate.
Brown said the caller gave no indication as to what kind of explosive device would go off. She said the department often takes calls about bomb threats at other parts of the city, but has not had any at City Hall in recent years.
Lalo Perez, the city's director of the Administrative Services Department, recalled an incident about 15 years ago in which a suspicious briefcase filled with wires prompted city officials to evacuate the whole building and bring in the bomb squad.
The briefcase belonged to a Pacific Bell employee, who visited the building for a service call. The worker forgot that he left the briefcase upstairs and waited outside with the city workers while the bomb squad was detonating his briefcase.