NEW ORLEANS (Reuters) - The National Football League was still working with New Orleans officials on Monday to determine what caused the power outage at Sunday's Super Bowl at the Superdome, so far dismissing any connection with the Beyonce halftime show.

With a record U.S. television audience watching along with viewers in 180 countries, about half the stadium lights went dark early in the second half of the game, in which the Baltimore Ravens defeated the San Francisco 49ers, 34-31.

NFL commissioner Roger Goodell told reporters on Monday an investigation was under way to determine the cause of the 35-minute disruption but one possible explanation had already been eliminated.

"There's no indication at all that this was caused by the halftime show," Goodell said. "I know that's out there, that Beyonce's halftime show had something to do with it. That is not the case from anything we have at this point."

Entergy Corp, the utility providing power to the Superdome, said its distribution and transmission feeders were serving the Superdome at all times.

Early indications were that the outage resulted from an abnormality in the Superdome's power system but it was too early to speculate on what went wrong, said Doug Thornton, senior vice president of the Superdome's management company, SMG.

A piece of equipment designed to monitor electrical load sensed an abnormality in the system where the Superdome equipment intersects with Entergy's feed into the building, triggering an automatic cut in power, SMG and Entergy said in a joint statement.

There was never any concern the power could not be restored, but it took time because of the size of the stadium and the complexities of the power system, Thornton said.

"We had people in place that could quickly work to restore power. We had experts on site, as we normally do when we have big events like this, our electrician, our electrical consultants were there and we were able to quickly work on that," Thornton said.

"There were no injuries, people remained calm, we had a pre-programmed announcement that was actually played. These are things that we actually drilled for."

None of the players or coaches said the stoppage had any impact on the game, and Goodell said the power problem would not adversely affect future bids by New Orleans to stage the Super Bowl, the United States' most-watched sports event.

"I fully expect that we will be back here for Super Bowls," Goodell said. "I hope we will be back. We want to be back ... I don't think this will have any impact at all on what I think will be remembered for one of the greatest Super Bowl weeks."