According to KTLA5 on July 20th:

A power outage in Castaic on Monday night temporarily left 1,747 people in the dark following an explosion and underground fire that were possibly caused by an incident involving an electrical vault, a Los Angeles County fire official said.

The fire was reported at 8:19 p.m., according to fire Supervisor Ed Pickett. It was burning in the area of Parker and Ridge Route roads, said Paul Netter, a spokesman for Southern California Edison.

Sky5 video showed flames emanating through a manhole after its cover was blown off in the explosion. A plume of smoke rose from the hole after firefighters used hoses to douse the fire with water.

Edison repair crews responded to the scene and assessed the problem that led to the power outage, according to Netter.

Electricity was restored to all but three customers by 1:30 a.m., according to the utility’s website.