Reuters.comRegister . Register now for FREE UNLIMITED ACCESS Sept 13 (Reuters) – The FBI has informed Twitter Inc. (TWTR.N) of at least one Chinese agent working at the company, US Senator Chuck Grassley said during a Senate hearing on Tuesday, where a whistleblower testified in which there were new concerns about foreign interference. Influential social media platform. Peter “Muz” Zatko, a well-known hacker who served as Twitter’s chief of security until his firing in January, said some Twitter employees were concerned that the Chinese government would be able to collect data on the company’s users. Twitter has come under fire…