Kelly, known as "Mac Daddy," and Chris Smith, known as "Daddy Mac," made up the rap group Kris Kross, who were known for wearing their clothes backwards as they rhymed.
"It appears it may have been a possible drug overdose," said Cpl. Kay Lester, a spokeswoman for the Fulton County police. Lester said that was based on statements received at the scene as well as evidence turned up at Kelly's home in south Atlanta.
According to Lester, police were called to Kelly's home at around 4:30 p.m. Wednesday. He was then transported to the south campus of the Atlanta Medical Center.
Investigator Betty Honey of the Fulton County Medical Examiner's office said Kelly was pronounced dead at the hospital at around 5 p.m. Wednesday.
No official cause of death has been determined, pending an autopsy.
Kris Kross was introduced to the music world in 1992 by music producer and rapper Jermaine Dupri after he discovered the pair at Greenbriar Mall in southwest Atlanta.
"To the world Chris was Mac Daddy but to me, he was a son I never had..." Dupri said in a statement Thursday.
"When I think about it, I spent more time with Chris and Chris than damn near anybody in my whole life, so you can imagine how bad this hurts," Dupri added. "I will always love you Chris, and I will never let the world forget you, may God bless your soul."
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 United States 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."
In 2009, after photos surfaced that showed him with bald spots on his head, there were rumors that he had cancer. But in an interview posted on YouTube by Straight from the A TV, he said he suffered from alopecia, a condition in which people lose their hair.
"My health is good, I just got alopecia, I don't have cancer, not other sort of diseases," he said.
Earlier this year, the group performed together to celebrate the anniversary of Durpri's label, So So Def.
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