A failed connection between an underground cable and a substation triggered the power outage in Belmont Wednesday night that left nearly 6,000 homes in the dark, a PG&E spokesman said Friday afternoon.
The outage, which initially affected 5,728 customers, was reported at 8:51 p.m., according to PG&E spokesman Joe Molica.
Crews were sent to the area and determined the majority of the outage was in underground circuits, he said.
By 10:18 p.m., crews had restored power to 4,913 customers. An additional 668 customers had their power back by 10:52 p.m., and the remaining 147 customers regained their power at 11:15 p.m.
Originally crews were unable to find a cause, but by 5 a.m. Thursday the cause was identified as a failed connection between an underground cable and a substation.
Molica said PG&E is still trying to determine what prompted the cable to fail.
"We know what caused the outage, but we don't know why that cable connector failed," he said.