Federal regulators probing Facebook for violations of antitrust law have considered seeking a preliminary injunction against the company, aiming to halt the tech giant’s plans to integrate its social-networking app with the other services it owns.

The legal move — described by a person familiar with the matter but not authorized to discuss a law-enforcement proceeding — would mark a major new threat for Facebook as the Federal Trade Commission forges ahead with an inquiry that has explored the competition concerns posed by its prior purchases of Instagram, a photo-sharing app, and WhatsApp, a messaging service.

FTC officials have not decided whether to take that course of action, the person said, which would require the commission to vote and then seek the permission of a court. The FTC and its Republican chairman, Joe Simons, declined to comment for this article, as did Facebook.

For now, some competition experts said that the FTC could be hamstrung if it doesn’t seek to stop Facebook from integrating its services. Absent that, it could prove difficult to penalize or unwind the company, if the government later finds Facebook violated the law.

“If the FTC thinks it has a plausible basis for challenging Facebook’s previous acquisition of Instagram or WhatsApp, it is critical to seek an injunction to prevent Facebook from mixing all the key assets from these divisions,” said Gene Kimmelman, a senior adviser to the consumer group Public Knowledge and a former antitrust official at the Department of Justice.

“Without an injunction,” he said, “winning a case in court might prove fruitless, like trying to unscramble eggs.”

The Wall Street Journal first reported the possible FTC move.

For months, FTC investigators have probed whether Facebook has run afoul of federal competition rules, particularly in the way it has gobbled up — or battled back — its social media rivals. It is one of multiple investigations targeting the tech giant, which is weathering similar scrutiny from nearly every state’s attorney general.

Some regulators bristled when Facebook chief executive Mark Zuckerberg sketched out a new vision for the company’s services earlier this year — aiming to operate Facebook, Instagram and WhatsApp independently, but integrating them, so that users could talk to each other across the services. Zuckerberg described the changes as part of a pivot toward privacy, but experts saw in that planned overhaul a new way for Facebook to correlate data about users — one that might prove difficult for concerned competition regulators to unravel if they ever tried to break the company up.

Privacy and competition regulators in Ireland, Germany and throughout the European Union soon opened investigations, raising concerns that Facebook was flouting antitrust protections to the detriment of competition and consumers. Facebook’s longtime critics in the United States, meanwhile, urged the FTC to do the same.

“At a time when Facebook is under scrutiny for its monopoly power and its abuses of its power, to say it’s going to integrate these three platforms is just another monopoly grab,” said Sally Hubbard, the director of enforcement strategy at Open Markets Institute.