NEW ORLEANS — The company that supplied electricity to Super Bowl XLVII says the blackout that halted the game was caused by a device it installed specially to prevent a power failure.

But the utility stopped short of taking all the blame and said Friday that it was looking into whether the electrical relay at fault had a design flaw or a manufacturing defect.

The relay had been installed as part of a project begun in 2011 to upgrade the electrical system serving the Superdome in anticipation of the championship game. The equipment was supposed to guard against problems in the cable that links the power grid with lines that go into the stadium.

“The purpose of it was to provide a newer, more advanced type of protection for the Superdome,” Dennis Dawsey, an executive with Entergy Corp., told members of the city council. Entergy is the parent company of Entergy New Orleans, the city’s main electric utility.

Entergy officials said the relay functioned with no problems during January’s Sugar Bowl and other earlier events. It has been removed and will be replaced.

All systems at the Superdome are now working, and the stadium was to host a major Mardi Gras event tonight, said Doug Thornton, an executive with SMG, the company that manages the stadium for the state.

The relay was installed in a building near the stadium known as “the vault,” which receives a line directly from a nearby Entergy substation. Once the line reaches the vault, it splits into two cables that go into the Superdome.

Sunday’s power failure cut lights to about half of the stadium, halting play between the Baltimore Ravens and San Francisco 49ers and interrupting the nation’s most-watched sporting event for 34 minutes.

Not long after the announcement, the manufacturer of the relay, Chicago-based S&C Electric Co., released a statement saying that the blackout occurred because system operators had put the relay’s so-called trip setting too low to allow the device to handle the incoming electric load.

The equipment was owned and installed by Entergy New Orleans.

“If higher settings had been applied, the equipment would not have disconnected the power,” said Michael J.S. Edmonds, vice president of strategic solutions for S&C.

Friday’s announcement appeared to absolve Superdome officials of any missteps. City officials had worried that the outage might harm New Orleans’ chances of getting another Super Bowl.