David McNew/Getty Images(CNN) - Toy giant Mattel disclosed late Thursday that the company received an anonymous whistleblower letter earlier this week and is now investigating the matter. Chris Sinclair stepped down in 2017 and was replaced by Margo Georgiadis, who Mattel hired from Google to help Mattel focus more on high-tech interactive toys. MGA Entertainment, the toy company that owns the Bratz and L.O.L. dolls, has also made several unsolicited takeover offers for Mattel that Mattel has rejected. The-CNN-Wire & 2019 Cable News Network, Inc., a Time Warner Company.