A 3D-printed Facebook logo is displayed in front of a US flag, March 18, 2018. REUTERS/Dado Ruvic/Illustration

WASHINGTON: The US Federal Trade Commission, a consumer and competition watchdog, is investigating Facebook after a major data scandal that affected 50 million users, US media reported on Tuesday.

A probe by the FTC would add further pressure on the social media giant which faces calls by Britain's Parliament and the European Commission for urgent investigations, while US lawmakers have called on Facebook founder Mark Zuckerberg to appear before Congress.

At the centre of the scandal is a British firm, Cambridge Analytica, which worked for Donald Trump's 2016 presidential campaign.

According to a joint investigation by The New York Times and Britain's Observer, Cambridge Analytica was able to create psychological profiles using data from 50 million Facebook users through the use of a personality prediction app that was downloaded by 270,000 people but also scooped up data from friends.

The goal was to be able to predict the behavior of individual US voters.

The Wall Street Journal reported that the FTC is probing whether, by the data transfer to Cambridge Analytica, Facebook violated terms of a decree under which it agreed to get user consent for collecting personal data and sharing it with others.

In a similar report, The Washington Post said that if the FTC ultimately finds that Facebook broke that agreement, it could fine the company $40,000 for each violation.

Facebook shares tumbled another 2.6 percent on Tuesday after a 6.8 percent plunge Monday on news of the scandal.

The social media company on Tuesday said it is "committed to vigorously enforcing our policies to protect people's information and will take whatever steps are required to see that this happens".