Fire crews were dispatched around 11:05 a.m. to reports of thick smoke coming from an underground vault at the intersection of 16th Street and Rondel Place, according to San Francisco fire personnel.
The fire department's Carbon Dioxide Unit were able to get the smoke and fire under control and worked with PG&E personnel to prevent further damage to the electrical vault.
The blaze caused 125 PG&E customers in the area to lose power, utility spokeswoman Jana Morris said.
As of 12:45 p.m., there was no estimate for when power would be restored.
Police are directing traffic around the manhole covering the vault, which is in the middle of the intersection, he said. No injuries have been reported.