Singer R. Kelly has been arrested on federal sex trafficking charges ... TMZ has confirmed.
According to law enforcement officials, Kelly was arrested Thursday in Chicago on charges contained in a 13-count indictment returned Thursday in the Northern District of Illinois. The indictment includes charges of child porn and obstruction of justice.
TMZ broke the story ... the family of Joycelyn Savage-- one of Kelly's live-in girlfriends -- provided detectives in New York with "physical evidence" and information on witnesses to Kelly's alleged crimes as well as those who were closely associated with the singer.
Story developing ...