A toxicology screening revealed that Kelly, 34, had a mixture of drugs in his system when he was pronounced dead on May 1, said Betty Honey of the Fulton County Medical Examiner's office in Atlanta.
Paramedics found Kelly unresponsive on a living room couch at his Atlanta home and tried to resuscitate him. Kelly, known as "Mac Daddy," was later pronounced dead at a local hospital.
Honey said she did not know which specific drugs Kelly had used before his death. However, a police report from the night of Kelly's death said his mother told investigators her son used cocaine and heroin the night before he died and had a history of drug abuse.
Kriss Kross was introduced to the music world in 1992 by music producer and rapper Jermaine Dupri after he discovered the pair at a mall in southwest Atlanta. Kelly performed alongside Chris Smith, who was known as "Daddy Mac." The duo wore their clothes backward as a gimmick, but they won over fans with their raps.
Their first and most successful song was the 1992 hit "Jump," which became a chart-topper in the United States and around the world. The two were never able to match the tremendous success of their first song, though they hadother hits like "Warm It Up," and "Tonite's tha Night."
At a memorial ceremony for Kelly in early May his uncle, Lemar Williams, said Kelly showed a love for music from an early age and mimicked Michael Jackson's dance moves. Williams said Kelly loved Atlanta and never wanted to live anywhere else.
Earlier this year, Kriss Kross performed in Atlanta to celebrate the anniversary of Dupri's record label So So Def and Williams said Kelly was planning to make a comeback.