Facebook falls 6 percent amid US investigation

Facebook's stock fall more than 6 percent Monday after the Federal Trade Commission (FTC) announced it is investigating the worst data leak in the company's history.

"The FTC takes very seriously recent press reports raising substantial concerns about the privacy practices of Facebook," the commission said in a statement referring to U.K.-based Cambridge Analytica's use of 50 million Facebook users' information without consent.

"Today, the FTC is confirming that it has an open non-public investigation into these practices," the statement said.

Facebook's stock suffered massive losses last week after news of the data leak, and the slide continued Monday.

Shares plunged to as low as $149.12 at 11.20 EST (1520GMT) after closing Friday at $159.39.

The company's stock lost 19.4 percent since last Monday, resulting in approximately $103 billion in losses in its market capitalization. The firm's market value was approximately $432 billion at 11.20 EST.

Founder and CEO Mark Zuckerberg saw his personal net worth fall to almost $60 billion during that time. He began last week at $74.5 billion.

Facebook faced more allegations Saturday when tech news website Ars Technica reported the social network saves call logs, names, phone numbers, texts, and messages of its Android users going back for years.

"This is not the case," Facebook replied in a statement that said call and text history logging is part of its Messenger application that helps users stay connected with friends.

The company said users who no longer wish to use the feature can turn it off at their settings.