Facebook and other big technology companies — Google, Apple and Amazon — have been under growing scrutiny for how they are wielding their power. Facebook has attracted particular attention for its dominant position in social networking and how it bought smaller rivals such as Instagram and WhatsApp over the years, which buttressed its lead.

In July, Facebook disclosed that the F.T.C. was investigating it over antitrust concerns. The Justice Department, Congress and state attorneys general are also examining whether Facebook has acted anticompetitively.

Leading antitrust academics and others have laid out a case to regulators for breaking up Facebook by unraveling its acquisitions of Instagram and WhatsApp. They have argued that the company made “serial defensive acquisitions” to protect its edge in the market for social networks.

But seeking an injunction of this kind would be an uncommon step for a federal antitrust agency because officials rarely consider unwinding mergers that have already closed. A majority of F.T.C. commissioners would need to approve the move in a formal vote, said an agency official who was not authorized to speak publicly.

The agency would also face a high bar in court to show that Facebook was about to violate antitrust laws or already had, this person said. A court is unlikely to issue an injunction simply to give the commission more time to investigate, the person said.