The U.S. government is officially investigating Facebook.
"The FTC takes very seriously recent press reports raising substantial concerns about the privacy practices of Facebook," said Tom Pahl, acting director of the FTC's Bureau of Consumer Protection. "Today, the FTC is confirming that it has an open non-public investigation into these practices."
News broke earlier this month that Cambridge Analytica, a data firm with ties to President Donald Trump's campaign, reportedly accessed information from about 50 million Facebook users without their knowledge.
CNN reported last week that the FTC was sending a letter to Facebook with questions about how the social media company allowed the data to wind up in the hands of Trump campaign consultants.
Facebook stock was down 4% in early trading Monday.
Reps for Facebook did not immediately respond to a request for comment.