Prince died from an opioid overdose ... it's now official from the Midwest Medical Examiner's Office, and the drug is even more powerful than Percocet.The M.E. performed toxicology tests on the singer and determined the singer died of an accidental overdose of Fentanyl -- a powerful synthetic opiate that is more potent than morphine ... often used for cancer patients to deal with severe pain. Fentanyl is often used to treat people who have developed a tolerance to less powerful opiates such as Percocet and morphine.