Apple and five major e-book publishers are being probed by the European Commission over worries that the parties have colluded to restrict competition in the market for e-books, reports Associated Press. The Commission issued the following statement:

Adamant to determine whether e-book publishers worked to fix prices, the Commission said it will be taking a closer look at the agreements between Apple and e-book retailers that define the retailer’s cut of the profit, price points and other business terms. Earlier this year in March, the Commission conducted a raid of the offices of several e-book publishers. Apple, as you know, operates iBookstore that sells e-books for iOS devices and keeps 30 percent of the proceeds to itself.

The five e-book publishers being scrutinized: Hachette Livre, a unit of France’s Lagardere Publishingl; Harper Collins, owned by Rupert Murdoch’s U.S.-based News Corp.; CBS Corp.’s Simon & Schuster; Penguin, owned by U.K. publishing house Pearson Group; and Germany’s Verlagsgruppe Georg von Holzbrinck.