A weekend autopsy on the body of Rick James [ tickets ], who died in his sleep on Friday morning (8/6) at his Los Angeles home, failed to turn up the cause of the soul artist's death.

James' three children, via a statement issued by a publicist, said they believe their father died of heart failure. The Los Angeles County Coroner's office reportedly is awaiting results of toxicology tests to determine whether James--who had a history of drug abuse before he cleaned up in the wake of legal and health problems--had any drugs in his system that may have contributed to his death. Results of the tests may not be available for up to 10 weeks.

Though he was just 56 years old at the time of his death, James was not in good health. He had diabetes, he suffered a stroke in 1998 and he wore a pacemaker.

A public viewing is scheduled for 5-8 p.m. Pacific Time Wednesday (8/11) at Forest Lawn Memorial Park-Hollywood Hills in Los Angeles. A memorial service is planned for 11 a.m. on Thursday (8/12) at the same location.