A preliminary report by the National Transportation Safety Board showed the outage increased pressure in the line shortly before the blast.
However, officials have not determined the exact cause of the disaster.
Investigators said that after the power failure, pressure increased by 15 pounds-per-square-inch 11 minutes before the blast in a San Bruno neighborhood.
The blast killed eight people and destroyed 37 homes.
Officials are apologizing this week for an emergency telephone alert in East Palo Alto that warned residents of another pipeline explosion. an operator mistakenly repeated last month's alert.
The Associated Press Contributed to this report.