WASHINGTON — The Justice Department could broaden its efforts to bring technology giants to heel, going beyond investigating potential antitrust violations to potentially challenge companies like Google and Facebook on multiple fronts, the deputy attorney general, Jeffrey A. Rosen, warned on Monday.

“We do not view antitrust law as a panacea for every problem in the digital world,” Mr. Rosen said during a speech in Washington at an American Bar Association antitrust forum. “We will not ignore any harms caused by online platforms that partially or completely fall outside the antitrust laws.”

The remarks were Mr. Rosen’s most significant on the Justice Department’s broad look at the technology sector, whose largest companies are dominant forces in communications, entertainment, news, advertising and commerce. The department has been engaged in an in-depth antitrust review and is working with state attorneys general to determine whether companies like Facebook have obtained too much market power.

Mr. Rosen said law enforcement officials could also use legal tools that touched on areas including privacy, consumer protection and public safety as part of a broader investigation into the role that online platforms play in the lives of consumers. Google, for example, dominates the online advertising market, and its operating system is found in a majority of smartphones around the world.