Natural causes can be a VERY LOOSE definition.
Someone does the "Scarface" routine and snorts an outrageous amount of coke, their heart speeds up and will basically explode from too much shit. But it's called a heart attack on the medical report...the toxicology report will say he had cocaine in his system while the medical examiner will probably report death due to a heart attack.
Like another poster said, I'd like to read the report.