Update 9:39 p.m.
As crews labored to replace a failed underground component that knocked out power to 1,925 customers in Walnut, the city of Diamond Bar experienced an outage that darkened SCE officials told Patch.
The outage was reported in the 22700 block of East Golden Springs Drive, near Grand Avenue, about 7:30 p.m., Southern California Edison spokesperson Scott Andresen told Patch.
Some 1,444 customers lost power, Andresen said, but 161 customers had it restored by 7:35 p.m.
There were still 1,283 customers without lights, however, including City Hall at 21810 Copley Drive, Andresen told Patch.
Update 9:02 p.m.
A failed component on some underground equipment caused the power to fail for 1,925 customers Friday, a Southern California Edison spokesperson said.
Power was restored to all but 18 customers by 8:30 p.m., SCE spokesperson Scott Andresen told Patch in a telephone interview.
Electricity was cut about 4:30 p.m. to an area bounded by La Puente Road to the south; Stockton Pass Road to the north; North Grand Avenue to the east and Arbor Ridge Drive to the west.
Crews were working to replace the component, Andresen said, but he could not estimate when all customers would have their lights back on.
Update: 6:44 p.m.
The estimated time for restoration of power to most customers is 9:30 p.m., according to the SCE outage website.
Two calls to an SCE representative for more details have remained unanswered.
Update: 5:42 p.m.
The estimated time for restoration of power is now undetermined.
Southern California Edison crews are trying to figure out why power went out in the Walnut area near Grand and Temple avenues.
The power went out around 4:30 p.m. Around 1,925 residents have been affected, according the the Edison website.
Electricity is expected to be restored by 6:30 p.m.