Nearly 13,000 residents were in the dark in Fullerton Monday night after a widespread power outage.
The power went out at homes and businesses shortly after 9 p.m..
Drivers were warned to take extra caution during a power outage, and treat every intersection as a four-way stop.
Power had been restored to all but about 100 customers by 3 a.m. Tuesday.
SoCal Edison is investigating the cause of the outage.