'No Tech Zone' sign in San Francisco befuddles residents

Alamo Square park officials say they did not post sign hung a half block from where a Google bus picks up employees as locals wonder if it is an artistic protest

San Francisco authorities are grappling with the mysterious appearance - and sudden disappearance - of an official-looking sign that warned visitors to a nearby park that they were entering a "No Tech Zone".

The sign was affixed to a concrete pole in San Francisco's Alamo Square on Monday, sparking a frenzied online discussion over who had erected it and why. By late Tuesday morning, however, the sign had vanished. Local officials are insisting they have no idea who erected the sign, or indeed who removed it.