Pacific Gas and Electric truck.
PG&E is reporting a large power outage in San Francisco's Castro neighborhood.
The outage was first reported at about 2:15 a.m. Wednesday.
At one time, PG&E's online outage map reported at least 5,000 customers were affected.
Utility crews worked on restoring power overnight, and the numbers of affected customers have been decreasing.
PG&E estimates service will be fully restored by 4:45 a.m..
The utility has not identified an official cause, but at least one person reported on social media of hearing a huge explosion.