Federal authorities have pulled the plug on their investigation of Duke ( DUK) Power. The Justice Department ended a yearlong probe of the giant utility without filing any charges against the unit or its employees. The government, which alerted Duke to its decision late Wednesday, began probing the utility after two state utility commissions determined the company had underreported regulated profits that -- when excessive -- can trigger a rate review. The commissions, located in Duke's core markets of North and South Carolina, began questioning Duke's profits three years ago after a company accountant blew the whistle on bookkeeping practices that significantly lowered regulated earnings. Following an independent audit by Grant Thornton, Duke agreed to pay both commissions a relatively modest sum to settle the disagreement. More than a full year after that settlement, Duke Power expressed relief on Thursday that the ordeal is finally over. "We are pleased that this review is complete and that this issue is now behind us," said Duke Power President Ruth Shaw. "The U.S. Attorney and grand jury have done a thorough and professional review of the regulatory issues, spanning more than a year and over 110,000 pages of Duke Power documents. We are gratified that they concluded there was no basis for further action or review." Defying a sectorwide slide, Duke inched up 11 cents to $21.71 on the decision. Despite the ruling, Duke whistleblower F. Barron Stone still believes the company engaged in questionable behavior. He nevertheless expressed little surprise that the government had decided to drop its case. "As I understand it, they needed to have irrefutable evidence -- and be certain of a conviction -- in order to move forward," Stone told TheStreet.com on Thursday. "I don't think the FBI opened up an investigation and examined 110,000 documents for kicks and giggles. But the question they had to ask was, 'Does this rise to the level of fraud?' Apparently, they weren't sure." Still, Stone believes some justice still has been served. "They had to give back some money," he pointed out. "Plus, they'll be watched with a much closer eye going forward. They shouldn't be able to pull any more shenanigans like they did before."