Following a similar announcement by the European Commission on Tuesday, the Department of Justice confirmed on Wednesday that it is also conducting an investigation into allegations that e-book publishers conspired with Apple to keep e-book prices from bottoming out. The DOJ has reportedly been investigating the situation for possible antitrust violations since publishers successfully pressured Amazon into adopting an agency model last year.

"We are also investigating the electronic book industry, along with the European Commission and the states attorneys general," Sharis Pozen, Acting Assistant Attorney General for the DOJ's Antitrust Division, said during a congressional hearing. Attorneys general for the states of Texas and Connecticut are also investigating the matter, according to the Wall Street Journal.

At issue is whether any antitrust violations occurred when Apple signed on several of the largest publishers to publish e-books through its iBookstore, which coincided with the launch of the iPad. Apple merely acts as an "agent" for the publishers, selling e-books at whatever price the publisher sets. Apple then takes its customary 30 percent cut as it does with music, movies, and apps.

Publishers seemed to relish having control over e-book pricing, as Amazon had been selling e-books below wholesale value in order to gain users for its Kindle e-reader device. When publishers asked Amazon to accept similar pricing arrangements, the company originally threatened to pull books from its inventory. However, Amazon eventually capitulated and made agency agreements for e-books among several large publishers.

A class-action lawsuit filed earlier this year accused publishers of being "terrified" that Amazon's discounting was depressing e-book prices, and therefore happily accepted Apple's agency model to keep prices high. It also accused Apple of being a willing partner to the conspiracy since its iPad would ostensibly compete with Amazon's Kindle (though it's worth noting that the recently released Kindle Fire is the first truly competing tablet from Amazon).

Given the number of simultaneous antitrust investigations, Apple's agreements with publishers will certainly get a fair amount of scrutiny. The publishers don't appear to be concerned, however. A spokesperson for Hachette told the WSJ that it "feels strongly that its decision to distribute e-books through agency distribution not only better serves our authors and customers, it has also helped to increase competition and consumer choice in e-books and devices."