The Super Bowl, the biggest US sports event of the year, was interrupted by a 35-minute power outage at the Superdome in New Orleans
Officials said the problem appeared to be with the electrical load coming into the stadium.
New Orleans electric utility Entergy Corp and the Superdome management company (SMG) said a problem with the "electrical load" caused a sensor to open a breaker.
This partially cut power to the dome "in order to isolate the issue," a safety feature that worked "as designed".
The abnormality in the electrical load happened where "the Superdome equipment intersects with Entergy's feed into the facility," according to a joint statement by Entergy and SMG.
The cause of the abnormality is unknown, they said.
After a half-time show by the singer Beyonce that was heavy on electric lights, Baltimore opened the second half with a 108-yard kickoff return for a touchdown that gave the Ravens a 28-6 lead early in the third quarter.
Moments later, the scoreboard and half of the overheard lights in the Superdome went out.
Officials waved a stop to play, which abruptly short-circuited the most watched television event of the year.
The overhead lights first went out on the San Francisco 49ers' side of the field before dimming in other parts, while overhead lighting remained on and kept the 72,968-seat stadium from being plunged into total darkness.
"Those things happen, and both teams had to deal with it," said Baltimore quarterback Joe Flacco, who was named Most Valuable Player.
After the outage, the 49ers staged a comeback and came close to defeating the Ravens, who won 34-31.
Entergy officials said no other parts of New Orleans were affected.
"The power outage was an unfortunate moment in what has been an otherwise shining Super Bowl week for the city of New Orleans," Mayor Mitch Landrieu said in a statement on NOLA.com.
"In the coming days, I expect a full after action report from all parties involved. For us, the Super Bowl isn't over until the last visitor leaves town, so we're focused on continuing to show our visitors a good time."
Superdome spokesman Eric Eagan did not speculate on the cause of the outage.
"We sincerely apologise for the incident," he said in a statement on NFL.com.
The Super Bowl, which determines the NFL champion for the 2012 season, is broadcast live in more than 180 countries and in more than 30 different languages.
CBS, the official broadcaster, charged advertisers an estimated $3.7 million to $3.8 million for 30-second spots in this year's Super Bowl.