made the agreement last October , which filed a lawsuit against Google in 2005, claiming copyright infringement, after the search giant began scanning books so the text could be searched online.
Under terms of the deal, Google would have the right to show content from books that are still in copyright but are no longer in print.
The $125m settlement, which still requires court approval, was paid to cover legal fees and to establish a registry for publishers or authors to get paid when their titles are used online.
Authors and publishers may opt out of the proposed settlement. If they don't, they will be considered part of it.
A judge has given authors four more months to decide whether to participate.
However, Justice Department officials are now looking into whether the agreement violates antitrust laws.
The Justice Department's request for information is a strong sign that it may seek to block or force renegotiation of the settlement.
Opponents of the agreement believe it would give Google broad copyright immunity.
Currently, users of Google Book Search are able to view snippets of books online. If the settlement is cleared by the Justice Department, Google will be able to make whole pages of copyright works available online.