The explosion was reported around 6:53 p.m. Saturday in the 18900 block of Parthenia Street, according to the Los Angeles Fire Department. It was reported in a high voltage electrical equipment area of the facility.
Viewers on social media reported outages in Porter Ranch, Winnetka, West Hills, Canoga Park, Woodland Hills, Granada Hills, North Hills, Reseda and Chatsworth. Many people also saw the large black plumes of smoke billowing from the facility.
At least 140,000 customers were without power in Northridge, Winnetka, Reseda, Lake Balboa, Tarzana, North Hills, Granada Hills, Chatsworth, West Hills, Canoga Park and Woodland Hills, according to LADWP around 7 p.m.
By 10 p.m., at least 50,000 customers received electricity again, while crews worked to restore power to the remaining 94,000 customers. There was no estimation on a full restoration.
Los Angeles firefighters also rescued several people from elevators when the power went out, but it was unclear how many people.
In many areas of the Valley, lights were out at intersections, businesses and homes.
"All of the sudden there was no power, which was always fun. But you figure it's a hot day, everybody has their air on. It's when I keep hearing the sirens, and then you look outside and there is smoke and then there's a lot of smoke. That's when you're like, 'Ok, something bad happened,'" Northridge resident Joyclyn Dunham said.
Customers in the affected areas said their night was uncomfortable because they are without any air conditioning as temperatures still hovered in the 90s.
Firefighters could not pour water on the fire because it was burning in 60,000 gallons of mineral oil, which is used in the cooling process at the center.
LADWP responded to the incident on Twitter, saying power had been cut off to the facility as a safety precaution and that it served the northern portion of the San Fernando Valley.
The facility, called Receiving Station J (RS-J) is part of an energy transmission system, according to the LADWP. The utility said the extent of the damage from the fire and explosion has yet to be assessed.
There were no injuries to any LADWP workers or firefighters at the scene.
The cause of the explosion was unknown, but temperatures were in the triple digits across the Valley.