People Magazine reported that the chief medical examiner in the case said the 20-year-old died of "unnatural causes," but that could include a heart attack, said the magazine's staff editor Larry Sutton.
The Nassau Guardian reported Monday that Smith died of a heart attack.
"Anna Nicole is absolutely devastated by the loss of her son. He was her pride and joy and an amazing human being. Please do not make any press inquiries at this time so that Anna Nicole can grieve in peace," read a statement on Smith's Web site.