An autopsy for Kelly found no signs of foul play or trauma, the Fulton County Medical Examiner said in a statement. Results from a toxicology report will available in three to four weeks.
Kelly had an extensive history of drug abuse, Kelly's uncle told police, according to their report.
The Kris Kross duo of Kelly and Chris "Daddy Mac" Smith was best known for "Jump" which topped the mainstream U.S. music charts in 1992 when Kelly and Smith were both 13 years old.
The duo, whose pants and shirts backward look was mimicked by fans, never scored a top 10 U.S. hit after "Jump" and released their third and final studio album, "Young, Rich & Dangerous," in 1996.
"To millions of fans worldwide, he was the trendsetting, backwards pants-wearing one-half of Kris Kross who loved making music," Kelly's family said in a statement. "But to us, he was just Chris - the kind, generous and fun-loving life of the party."
Hip-hop music mogul Jermaine Dupri, who discovered the group and produced many of their songs, called Kelly the "son I never had" in a statement posted online.
"I will always love you, Chris, and I will never let the world forget you, may god bless your soul," Dupri said.
With files from Reuters
