San Diego

A mysterious plume of smoke triggered an unofficial evacuation of the San Diego County Courthouse on Thursday, but fire investigators were unable to find the source of the fumes. About 100 people left the first floor of the courthouse. However, the trial of Mayor Roger Hedgecock continued without interruption. The scare lasted about half an hour, Fire Department spokesman Ron Davis said. Initially, fire investigators speculated that an escalator motor might have burned out because the escalators had stopped. Later, they concluded that fire alarms had triggered the shutdown. Both fire personnel and maintenance crews remained mystified by the incident late Thursday, according to Clarence Kaufman, assistant director of the county Department of General Services.