Autopsy results from the U.S. pop star Prince, who died suddenly in April, show he died of an accidental overdose of fentanyl, a powerful opioid painkiller more potent than morphine or heroin.
It was not immediately clear if the drug was obtained illegally or by prescription. The medical examiner's report, released Thursday, said the overdose was self-administered and accidental.
Prince, whose full name was Prince Rogers Nelson, was found dead at his Paisley Park mansion outside Minneapolis on April 21. His death came less than a week after he was given emergency treatment with Narcan, an antidote used for opiate overdoses.
Prince's hometown newspaper, the Minneapolis Star-Tribune, reported the musician had seen a family practitioner the day before his death for treatment for opioid withdrawal symptoms. The same day, Andrew Kornfeld, son of prominent addiction specialist Howard Kornfeld, took an overnight flight from California to Minnesota to meet with the musician. Reports say Kornfeld was at the mansion when Prince's body was found.
Kornfeld was carrying a supply of buprenorphine, a drug that can be used to treat opioid cravings and withdrawal symptoms when a user is being weaned off the drug.
Fentanyl is similar to morphine and can be used when patients have developed a tolerance to other opioid medications.
It has also been blamed for an uptick in heroin overdoses in recent months. Experts say drug dealers are cutting fentanyl into heroin to make a more potent drug.
The U.S. Drug Enforcement Administration received reports of more than 700 fentanyl-related overdoses in late 2013 and in 2014.
Earlier reports said Prince, who reportedly did not drink or use recreational drugs, had the painkiller Percocet in his system when he died.
Friends of the 57-year-old musician said he suffered joint pain after years of performing vigorous stage shows.
If investigators find that Prince was sold fentanyl illegally, the person or persons who sold it to him could be charged with state and federal crimes resulting in up to 25 years in prison.