SAN FRANCISCO -- City and utility officials vowed Friday to prevent a recurrence of two blackouts that struck Candlestick Park during "Monday Night Football."
Pacific Gas & Electric Co. said the initial blackout that delayed the start of the game by about 20 minutes occurred when a wire that carries the stadium's main power supply broke, creating a display of sparks shown during ESPN's nationally televised broadcast.
San Francisco Mayor Ed Lee said the second blackout that stopped play for about 15 minutes in the second quarter was caused by a malfunctioning switch involving the backup power supply.
In a letter to the 49ers, PG&E president Anthony Earley said the company was fixing the failed line and installing monitoring equipment, and will perform a test to ensure the lights stay on if it is necessary to switch to backup power.
Technicians also are performing tests on the splice sleeve that failed and caused the line to break in two, Earley said.
In a separate letter to the 49ers, Lee said crews were replacing the switch that caused the second blackout and would perform tests to ensure it functions properly.
The blackouts overshadowed the 49ers' dominating 20-3 win over the Pittsburgh Steelers that preceded the 49ers' return to the postseason for the first time since 2002 under rookie coach Jim Harbaugh.
The power failure also brought renewed attention to the 49ers' intention to move the team out of 51-year-old Candlestick to a new stadium outside city limits in nearby Santa Clara, which has secured most of the financing needed to build a new venue.
The 49ers are on the road for their last two regular-season games but are assured of playing at least one playoff contest at Candlestick.
Team officials said they were confident the blackouts, which Lee called a "national embarrassment," won't recur.