The Justice Department is opening an antitrust investigation into the biggest online platforms over whether they've been stifling competition.

No companies were named, but the investigation will consider public concerns regarding "search, social media, and some retail services online," the Justice Department said on Tuesday. The review will focus on how the biggest online platforms have achieved and maintained their market power, and whether the practices have harmed consumers.

"Without the discipline of meaningful market-based competition, digital platforms may act in ways that are not responsive to consumer demands," said Assistant Attorney General Makan Delrahim of the department's antitrust division, which is overseeing the investigation.

The review is bound to pull in Amazon, Facebook, and Google, which have all faced accusations of anti-competitive behavior and holding a monopoly in the internet industry. Last November, President Trump himself said his administration was considering an antitrust investigation into the three companies.

The Justice Department's announcement also indicates the probe will be quite broad, and take into account input from consumers and businesses. "The Department's Antitrust Division is conferring with and seeking information from the public, including industry participants who have direct insight into competition in online platforms, as well as others," it said.

"If violations of law are identified, the Department will proceed appropriately to seek redress," the Justice Department added.

Apple will also probably be ensnared in the probe. The company has recently faced growing scrutiny over its control of the iOS App Store, which is the only official destination to download apps for your iPhone.