Investigator Betty Honey of the Fulton County Medical Examiner's office said Kelly was pronounced dead around 5 p.m. Wednesday at the south campus of the Atlanta Medical Center.
Honey said authorities are unsure of Kelly's cause of death and that an autopsy has yet to be performed.
Kelly, known as "Mac Daddy," and Chris Smith, known as "Daddy Mac," were introduced to the music world in 1992 by music producer and rapper Jermaine Dupri after he discovered the pair in an Atlanta mall. The duo wore their clothes backwards as a gimmick, but they won over fans with their raps.
Their first, and by far most successful song, was "Jump." The hit, off their multiplatinum 1992 debut album Totally Krossed Out, featured the two trading verses and rapping the refrain, the song's title. The duo had surprising maturity in their rap delivery, though the song was written by Dupri. It would become a No. 1 smash in the U.S. and globally, and one of the most popular of that year.
Their success led to instant fame: They toured with Michael Jackson, appeared on TV shows, and even had their own video game.
The group was never able to match the tremendous success of their first song, though they had other hits like "Warm It Up," and "Tonite's tha Night."
Earlier this year, the group performed together to celebrate the anniversary of Durpri's label, So So Def.