NEW ORLEANS (AP) — An electrical device that had been installed expressly to prevent a power outage caused the Super Bowl blackout, the stadium's power company said Friday as it took the blame for the outage that brought the game to a halt for more than a half-hour.

Officials of Entergy New Orleans, a subsidiary of New Orleans-based Entergy Corp., said the device, called a relay, had been installed in switching gear to protect the Superdome from a cable failure between the company's incoming power line and lines that run into the stadium.

The switching gear is housed in a building known as "the vault" near the stadium that receives a line directly from a nearby Entergy power substation. Once the line reaches the vault, it splits into two cables that go into the Superdome.