The US Federal Trade Commission is investigating Facebook's privacy practices following a week of scandals including whether the company engaged in "unfair acts" which cause "substantial injury" to consumers.
Facebook's stock, which already took a big hit last week, plunged as a result.
The social media giant said the company remains "strongly committed" to protecting people's information and that it welcomes the opportunity to answer the FTC's questions.
News outlets reported on the FTC investigation last week, but the FTC had not confirmed it until Monday.
Facebook reached a settlement with the FTC in 2011 offering privacy assurances.