Officials of the utility company supplying power to the Superdome say the Super Bowl outage occurred when sensing equipment detected an "abnormality" in the system.
A statement from Entergy and the Superdome said Sunday that a piece of equipment monitoring electrical load sensed the abnormality and opened a breaker, partially cutting power.
The statement said backup generators kicked in before full power could be restored.
The Baltimore Ravens were leading the San Francisco 49ers 28-6 when most of the lights in the 73,000-seat building went out with 13:22 left in the third quarter.
Auxiliary power kept the playing field from going totally dark, but escalators stopped working and the concourses were only illuminated by small banks of lights tied in to emergency service.
Philip Allison, a spokesman for Entergy New Orleans, which provides power to the stadium, said power had been flowing into the stadium before the lights failed.
"All of our distribution and transmission feeds going into the Superdome were operating as expected," Allison said.
The outage appeared to originate in a failure of equipment maintained by stadium staff, he added.
The power failure occurred shortly after Jacoby Jones returned the opening kickoff of the second half for a touchdown, giving the Ravens a commanding lead.
The public address announcer said the Superdome was experiencing an interruption of electrical service and encouraged fans to stay in their seats. Some fans did the wave to pass the time. Players milled around on the sidelines, some took a seat on the bench, other on the field. A few of the Ravens threw footballs around.
Officials gathered on the field and appeared to be talking to stadium personnel. Finally, the lights came back on throughout the stadium and the game resumed.
The outage provided a major glitch to what has largely been viewed as a smooth week for New Orleans, which was hosting its first Super Bowl since 2002 and was eager to show off how the city has rebuilt since Hurricane Katrina.
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