Pacific Gas and Electric Company restored power yesterday afternoon to approximately 40,000 customers after transmission breakers at the company's Martin Substation opened, causing outages concentrated in San Francisco's Financial District and the Cow Palace area of the peninsula. The initial event occurred at approximately 1:30 p.m., and power was restored to all affected customers by approximately 3:30 p.m..

PG&E crews were working through the evening in an effort to determine precisely what caused the transmission breakers to open. The company has dispatched additional personnel to the substations affected to monitor operations this evening while teams inspect equipment.

At approximately 2:30 p.m., PG&E received reports of an underground explosion on Mission Street between First and Second Streets. Inspection showed that a subsurface transformer failed. However, contrary to preliminary indications, updated reports indicate that this event was not the initiating cause of the larger outages. The company is investigating the cause of the transformer failure.