The Justice Department antitrust division has sent at least two publishers the civil equivalent of a subpoena, seeking information on a deal reached with Google, the Wall Street Journal reported on Tuesday.
The class action settlement concerns copyright and gives Google, which has been scanning books, the right to digitize and sell entire libraries.
The Journal said that David Young, chief executive officer of Lagardere SCA's Hachette Book Group, confirmed that the company had received a civil investigative demand, or CID, which is the civil equivalent of a subpoena.
No one was available at Hachette to confirm the report and the journal did not say what Justice wanted to know.
The Journal said it had also reached a second publisher, who also confirmed receiving the CID, but declined to be identified.
Two experts on digitization told Reuters in April that the Justice Department was making inquiries about the settlement.
Google agreed to pay $125 million to create a Book Rights Registry, where authors and publishers may register works and receive compensation from institutional subscriptions of book sales.
The Google plan is to let readers search millions of copyrighted books online, browse passages and purchase copies.
The deal would also allow Google, and no one else, to digitize so-called orphan works. Those books are covered by U.S. copyright law but it is unclear who owns the rights to them.
The deal is being reviewed by a U.S. District Court.
(Reporting by David Lawsky; Editing by Gary Hill)