The Green Mile star died suddenly on Monday (September 3), aged 54.
Craig Harvey, a representative of the LA County coroner's office, told the Los Angeles Times on Tuesday afternoon (September 4) that there were no factors prompting a coroner's review.
He also said that a doctor had signed off on Duncan's death certificate.
It is believed that the Oscar-nominated actor had not fully recovered from a heart attack sustained in July of this year.
Duncan's fiancée Omarosa Manigault-Stallworth has been quoted as saying that she is "devastated" by the death of the man she dubbed "the love of my life".
Photo gallery - Michael Clarke Duncan's career in pictures:
Copyright: Rex Features Moviestore Collection