The Jamaican-born hip-hop artist and producer died last week. He was 44.
The Los Angeles Times said the autopsy proved inconclusive and officials are waiting for the results of toxicology tests to come in before they determine the cause of his death. It could take several weeks for the test results to be completed and analyzed, the newspaper said.
Billboard.com quoted a spokesman for the Los Angeles County coroner's office as saying there were no illegal drugs found in Heavy D's Beverly Hills, Calif., home after his death.
He had been prescribed a drug for a cough that could have been pneumonia, the music Web site said.
TMZ said the star was 344 pounds at the time of his death.