At issue were some demo mobile phones that AT&T provided free to various viewing parties in Arkansas, the home state of winner Kris Allen.
A report from the Arkansas Post-Democrat, which was then picked up by The New York Times, said local AT&T representatives gave fans demo phones and instructed them how to send 10 free text-message votes at the touch of a button -- so-called "power" texting. AT&T said this promotion was only for two local viewing parties.
While "Idol" allows a viewer to vote as many times as possible during the entire singing competition, the show does prohibit "technical enhancements" to increase voting. AT&T is the only mobile network that can be used to cast "Idol" votes via text message.
On Wednesday, Fox and "Idol" producers Fremantle North America and 19 Entertainment said in a release: "Fox and the producers of "American Idol" are absolutely certain that the results of this competition are fair, accurate and verified. Kris Allen is, without a doubt, the American Idol."
"We have an independent third-party monitoring procedure in place to ensure the integrity of the voting process. In no way did any individuals unfairly influence the outcome of the competition."
For its part, AT&T said: "Last week, countless parties were held in homes, bars and other public places across America to watch the "American Idol" finale. In Arkansas, a few local AT&T employees were invited to attend two local watch parties organized by the community."
"Caught up in the enthusiasm of rooting for their hometown contestant, they brought a small number of demo phones with them and provided texting tutorials to those who were interested. Going forward, we will make sure our employees understand our sponsorship celebrates the competition, not individual contestants. That said, it's quite a leap to suggest that a few individuals could have impacted the final results."