Two U.S. senators said on Tuesday a Facebook Inc (FB.O) whistleblower will testify at a Senate hearing next week about what one of them called the social media company"s "toxic effects" on young users. "This whistleblower’s testimony will be critical to understanding what Facebook knew about its platforms" toxic effects on young users, when they knew it, and what they did about it," Democratic Senator Richard Blumenthal, head of a subcommittee of the Senate commerce panel, said in a statement announcing the Oct. 5 hearing. Senator Marsha Blackburn, the subcommittee"s top Republican, said: "From turning a blind eye to the negative impacts of its platforms on teens’ mental health to its inability to police for trafficking, domestic servitude, and other harmful content, Facebook has a lot to account for." Facebook did not immediately respond to a request for comment. The announcement came a day after Instagram, the photo-sharing service owned by Facebook, said it had hit a pause on a new app it is creating for children amid growing criticism from U.S. lawmakers and advocacy groups. read more The senators" statement did not give any information about the whistleblower. Editing by Cynthia Osterman Our Standards: The Thomson Reuters Trust Principles.