An autopsy Saturday failed to determine the cause of death for funk legend Rick James (search), authorities said. James, 56, died in his sleep Friday at his home near Universal City. The singer was a diabetic and also had a pacemaker. He suffered a stroke in 1998.

His three children — daughter Ty and sons Rick Jr. and Tazman — said Friday through a spokeswoman that they believe their father died of heart failure.

James had a history of cocaine addiction that led him to two assault convictions in the 1990s and a two-year stretch in prison.

Officials are awaiting results of a toxicology test (search), which could take several weeks, said Lt. David Smith, supervising investigator of the Los Angeles County coroner's office.

James's career peaked in 1981 with "Super Freak," a song so enduring that a strain of its infectious bass line powered the MC Hammer (search) hit "U Can't Touch This" nearly a decade later.

The song earned the Grammy for best R&B song in 1990 for both Hammer and James.

James had enjoyed a bit of a revival recently, in part because of comedian Dave Chappelle portraying him as violent and arrogant on his "Chappelle's Show." James himself appeared on the Comedy Central show.