ASPEN, Colo. — The U.S. government is forging ahead with its review of online platforms for potential antitrust violations, coordinating with state attorneys general while signaling it could send demands for documents to Silicon Valley companies and their critics, the chief of the Justice Department’s antitrust division said Tuesday.

In wide-ranging comments during a policy conference here, Assistant Attorney General Makan Delrahim also waded into a simmering Washington debate over what legal protections should be afforded to Facebook, Google and Twitter for the user-generated content that appears on their platforms, raising the possibility that Congress could re-examine the law.

For much of the tech industry, the DOJ’s broad antitrust review is the greatest challenge. Announced in July, department officials said the review would explore “widespread concerns that consumers, businesses, and entrepreneurs have expressed about search, social media, and some retail services online." While DOJ never mentioned any company by name, its concerns track closely with Google’s sprawling search empire, Facebook’s dominance in social media and Amazon’s position as the country’s e-commerce leader.

Asked about the next phase of the review, Delrahim said at a tech policy conference in Aspen that DOJ, in a “normal investigation,” would “seek documents and information from parties who might be affected,” adding: “We might be issuing compulsory process on some third parties who may or may not need it for whatever reason to provide more information to us.”

In the meantime, Delrahim said DOJ is communicating with state attorneys general, who for months have raised alarms that tech giants including Facebook and Google may be too big and pose a threat to competitors and consumers. Delrahim added it is “safe to say at least more than a dozen or so.... have expressed interest in the subject matter.”

Delrahim’s comments come two months after reports in the Post and others revealed the DOJ and the government’s other competition agency, the Federal Trade Commission, planned to intensify their antitrust scrutiny of the tech industry. In doing so, the agencies essentially divvied up oversight of Amazon, Apple, Facebook and Google, a process that sets the stage for investigations into specific business practices at each of those companies.

Facebook previously has acknowledged it is under investigation by the Federal Trade Commission, a probe believed to be focused on its previous acquisition of companies including WhatsApp and Instagram.

Delrahim said there are growing questions about large tech giants’ purchase of “nascent competitors” and the “intention of the incumbent” in gobbling up startups in the first place — but declined to say if it factored into the DOJ’s review.

Others in Washington have sought to target tech giants — and their power and size — by calling for reforms to a decades-old provision in federal law that shields companies from liability for the content posted by their users or the decisions they make over whether to leave it up or take it down. Delrahim said the portion of law, known as Section 230, isn’t an antitrust issue —but expressed support for reviewing it.

“I don’t think back when that law was passed the type of online information services that we see today was anticipated by Congress,” Delrahim said. “But we should take a look, at almost I think every law, but particularly this law, to see does it make sense?”

“I’m not a huge fan of private lawsuits.... but to the extent that companies internalize externalities of their offerings and make them improve and be more responsible, that can be a positive thing," he said. “So I think a review of Section 230 by those people who care about it is perfectly appropriate.”