James died Friday morning at his Los Angeles area home from what his children suspect was heart failure, the family publicist said, but the exact cause remains unknown.
Officials are awaiting the results of toxicology tests to determine if James, who had a history of partying and reportedly had recently returned to using cocaine, had drugs in his system, E! Online said.
Test results could take six to eight weeks, said a spokesperson for the Los Angeles County Coroner's office.
James was a diabetic who suffered a stroke in 1998. He had hip replacement surgery and a pacemaker inserted in his chest in recent years.
A public viewing is scheduled 5-8 p.m. Wednesday at Los Angeles' Forest Lawn Memorial Park, Hollywood Hills.
A memorial service is set for 11 a.m. Thursday.