NEW ORLEANS—The company that supplies electricity to the Superdome and the stadium's management company have hired an outside expert to investigate the cause of the power failure during the Super Bowl earlier this month.

Entergy spokesman Michael Burns said Friday that the utility and SMG have hired Utah-based forensic engineer John Palmer to perform an independent analysis of the outage.

Entergy has said it believes the outage was caused by an electrical relay device it installed specially to prevent a power failure at the dome. But a company official said it was looking into whether the device had a design flaw or a manufacturing defect.

The blackout affected roughly half of the stadium's lights and delayed the Feb. 3 game between the Baltimore Ravens and San Francisco 49ers for 34 minutes.