The US Federal Trade Commission (FTC) is preparing a case against Facebook.

The competition authority has been investigating the social media company for over a year, a source close to the investigation says in US media.

The FTC suspects that the tech giant has used its dominant market position to knock out competition.

The regulator has not yet confirmed the news because the investigation is confidential.

Critics argue that Facebook's takeover of Instagram and WhatsApp eliminated two companies that could have become major competitors.

At the time, the FTC investigated and approved both acquisitions.

However, the regulator may revise past decisions and take them to court.

The competition authority already questioned Facebook CEO Mark Zuckerberg last month in connection with the investigation. According to an insider, no final decision has yet been taken on what will happen next. In order for it to come to court, a majority of five FTC commissioners must be in favor of it.