North Carolina utilities regulators are hiring a former federal prosecutor and the Chicago law firm he heads to dig into whether they were misled ahead of the takeover creating America’s largest electric company.

The North Carolina Utilities Commission said Wednesday it has hired Anton Valukas and the Jenner & Block law firm to investigate what happened before regulators approved Charlotte-based Duke Energy Corp. taking over Raleigh-based Progress Energy Inc.

The companies completed their merger last month, days after North Carolina regulators approved. Hours after the deal was done, Duke Energy’s board ousted its long-promised CEO.

Valukas was the court-appointed examiner in the Lehman Brothers bankruptcy case. He found the investment bank hid $50 billion in debt before its 2008 collapse, which created a crisis that threatened the world’s financial system.