Jones died on Feb. 29 near his home in Indiantown, Fla.
The British-born singer had a severe build-up in his arteries, according to the report. The toxicology reports came back negative for any sign of drugs in his system cannabinoids, a class of drugs that includes marijuana. However, that played no role in his death.
The report also noted some congestion in the singer's lungs.
Jones quickly became a teen idol as a member of The Monkees, with hit songs including "Daydream Believer" and "I'm a Believer."