SAN FRANCISCO >> The utility that serves Candlestick Park is blaming San Francisco-owned equipment for the first of two embarrassing power failures during Monday Night Football.

NFL security chief Jeff Miller said he witnessed a transformer blow up while he was monitoring a gate outside the stadium, where a shooting during the preseason already put a negative light on this venue.

The first outage pushed back the opening kickoff by 20 minutes. Thousands of flashbulbs went off in the midst of the blackness, with a sellout crowd of 69,732 sitting in darkness — including all those Terrible Towel-waving Steelers fans who travel the country with their team.

The second delay came early in the second quarter and halted the game again between the playoff-bound teams for about 15 minutes. Miller and other NFL officials gathered in the press box to assess the situation, remaining in constant contact with the commissioner’s office.

Miller said he remained confident the game could be finished even using an alternative power source because the problem appeared to be outside the stadium.

"They told us that we were on the second feed, so if that feed would have been somehow interrupted then we probably wouldn’t have been able to get the lights back," Miller told The Associated Press.

"That’s why we’re operating in (the stadium) now. That’s why we’re playing, because we think that we’ll be able to continue. We hope to be able to continue. There’s probably a problem outside the stadium."

This marked the 49ers’ only Monday Night game this season and their final regular-season home game at Candlestick Park. The NFL certainly will want to make sure there are no problems when San Francisco hosts a home playoff game next month as NFC West champions.

Miller said he believes Candlestick can capably host a playoff game.

The power throughout the stadium went off about 25 minutes before the scheduled kickoff of 5:40 p.m. local time. The public address system stopped working along with everything else, so team officials encouraged media to use Twitter to reach fans and encourage them to sit tight and not panic. An emergency light quickly came on in a far corner of the stadium.

"What happened was the lights in the lots went out," Miller said. "And about two minutes later, the transformer blew and then we lost everything, other than the emergency lights inside."

A 49ers spokesman said city engineers worked swiftly to switch the power to backup generators.

Joe Molica, a spokesman for Pacific Gas & Electric Co. said the power company was still investigating the cause of the outage.

"So far I don’t know what the cause is," Molica said. "We do know that Candlestick was the only customer affected by this outage."

Molica said PG&E and park authorities had made all the routine checks earlier in the day and that all systems appeared to be in order.

He said was back up on full power and multiple crews went to Candlestick to investigate.

Monday marked San Francisco’s biggest home game since their last trip to the playoffs in January 2003, when the Niners came from behind to stun the New York Giants 39-38 in one of the greatest comebacks in NFL history.

San Francisco Mayor Ed Lee said city workers worked with PG&E officials to restore power to the stadium and he has called for an investigation "to prevent incidents such as this from happening again."

He also took the time to crow a bit over the 49ers win.

"Tonight we all share in tremendous pride for our San Francisco 49ers," he said. "We must make every effort to support continued victories for the team and fans across the Bay Area in the weeks ahead."

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AP Sports Writer Antonio Gonzalez and AP Writer Beth Brown contributed.