The Federal Trade Commission confirmed today that it has an opened a “non-public” investigation into Facebook Inc.’s privacy practices.

The social media giant’s stock quickly dropped more than 5 percent. It was down more than 20 percent from its Feb. 1 high.

The FTC’s announcement comes after reports last week that the agency was investigating Facebook over the widening controversy involving Cambridge Analytica. That data analytics firm tied to the Donald Trump presidential campaign accessed 50 million Facebook users’ information without those users’ knowledge, allegedly in an effort to influence voters.

Bloomberg News reported last week that the FTC was looking into whether Facebook had violated terms of a 2011 consent decree in which the tech giant agreed to get users’ permission for certain changes to privacy settings.

The FTC’s confirmation that it is investigating Facebook is the latest of the social media giant’s problems after the New York Times and British newspaper the Observer reported that Cambridge Analytica had aimed to use Facebook user data in an attempt to sway voter opinions.

The data originated from a personality quiz app developed in 2013 by a Cambridge University researcher. About 300,000 people took that quiz, and the researcher was also able to access “tens of millions of their friends’ data” based on how Facebook’s platform worked at the time, Facebook Chief Executive Mark Zuckerberg said last week in a post on his Facebook page.

Zuckerberg said he learned two years later from journalists at the Guardian that the Cambridge researcher had shared the data from his app with Cambridge Analytica, a move that violates Facebook policies. Zuckerberg said that Facebook banned the personality quiz app from its platform, demanded that the researcher and Cambridge Analytica “formally certify” they had deleted all of the improperly obtained data, and received those certifications.

Lawmakers have called for Zuckerberg to testify in front of Congress.

Facebook’s treatment of personal information has upset people and led to a #DeleteFacebook social media campaign. Several high-profile individuals, including singer Cher and SpaceX and Tesla CEO Elon Musk, have supported the campaign. SpaceX’s and Tesla’s Facebook profiles disappeared last week.