Nearly 9,000 DWP customers in Silver Lake and Westlake remained without power late Tuesday evening, and officials say electricity will not be restored until about 6:30 a.m. Wednesday.
The power outage was caused by a vault explosion in the 600 block of North Hoover Street, said Los Angeles Department of Water and Power spokesman Jason Stinnett.
Another 12,000 customers lost power earlier in the evening, but crews restored their service by 10:45 p.m., according to DWP officials.
It's unclear what caused the explosion, Stinnett said.
"These can blow up for any multitude of reasons," he said. No outages were reported in other sections of the city.
The power outages come after California officials asked residents statewide to reduce their energy consumption between 2 p.m. and 9 p.m. through Wednesday after a wave of triple-digit temperatures was forecast this week.
The California Independent System Operator issued the Flex Alert -- an electricity conservation call -- asking residents to voluntarily scale back power usage as demand on the state's grid will probably surge through Wednesday.