Tests on the dome's electrical feeders showed decay and "a chance of failure," state officials warned in a memo dated Oct. 15. Also, the utility that supplied the stadium with power expressed concern about the reliability of the service before the NFL championship.
Entergy New Orleans, the company that supplies the stadium with power, and the structure's engineering staff "had concerns regarding the reliability of the Dome service from Entergy's connection point to the Dome," the memo adds.
The memo — prepared for the Louisiana Stadium & Exposition District — says those concerns were due in part to "circumstances that have previously occurred with the electrical service regarding transient spikes and loads."
The memo also cited 2011 blackouts that struck Candlestick Park, where the San Francisco 49ers were playing a nationally televised Monday night football game, as a reason for ordering the tests.
Authorities later authorized spending nearly $1 million on Superdome improvements, including more than $600,000 for upgrading the dome's electrical feeder cable system.
"As discussed in previous board meetings, this enhancement is necessary to maintain both the Superdome and the New Orleans Arena as top tier facilities, and to ensure that we do not experience any electrical issues during the Super Bowl," said an LSED document dated Dec. 19.
The lights-out championship game proved an embarrassment for New Orleans just when it was hoping to show the rest of the world how far it has come since Hurricane Katrina in 2005. But many fans were forgiving, and officials expressed confidence that the episode wouldn't hurt the city's hopes of hosting the championship again.
To New Orleans' relief, NFL Commissioner Roger Goodell said the city did a "terrific" job hosting its first pro football championship in the post-Katrina era.
"I fully expect that we will be back here for Super Bowls," he said, noting a backup power system was poised to kick in but wasn't needed once the lights came back.
Fans watching from home weren't deterred, either. An estimated 108.4 million television viewers saw the Baltimore Ravens beat the San Francisco 49ers 34-31, making it the third most-viewed program in television history. Both the 2010 and 2011 games hit the 111 million mark.
As for possible culprits, it couldn't be blamed on a case of too much demand for power.
Meters showed the 76,000-seat stadium was drawing no more electricity than it does during a typical New Orleans Saints game, according to Doug Thornton, manager of the state-owned Superdome.
He also ruled out Beyonce's electrifying halftime performance. She brought along her own generator.
Officials with the utility and the Superdome were quick to note that an NFL game, the Sugar Bowl and another bowl game were played there in recent weeks with no apparent problems.
The problem that caused the outage was believed to have happened around the spot where a line that feeds current from Entergy New Orleans connects with the Superdome's electrical system, officials said. But whether the fault lay with the utility or with the Superdome was not clear.
Determining the cause will probably take days, according to Dennis Dawsey, a vice president for distribution and transmission for Entergy. He said the makers of some of the switching gear have been brought in to help figure out what happened.
Cinthia Hedge-Morrell, chairwoman of the New Orleans City Council's Utility Committee, called an emergency committee meeting Friday with Entergy representatives and others, seeking additional information.
The blackout came after a nearly flawless week of activity for football fans in New Orleans leading up to the big game.
Mayor Mitch Landrieu told WWL-AM on Monday that the outage won't hurt the city's chances, and he joked that the game got better after the blackout: "People were leaving and the game was getting boring, so we had to do a little something to spice it up."
The city last hosted the Super Bowl in 2002, and officials were hoping this would serve as the ultimate showcase for the city's recovery since Hurricane Katrina in 2005. The storm tore holes in the roof of the Superdome and caused water damage to its electrical systems, and more than $330 million was spent repairing and upgrading the stadium.
Sunday's Super Bowl was New Orleans' 10th as host, and officials plan to make a bid for an 11th in 2018.
Associated Press writers Beth Harpaz, Brett Martel and Barry Wilner contributed to this report.