Musician and singer Prince died of an accidental overdose of the powerful painkiller fentanyl, it has been revealed. A one-page report by the Midwest Medical Examiner's Office says the 57-year-old administered the drug himself, but it is not known when he took it. The office said it has completed its investigation and had no further comment to make. Prince was found dead at his Paisley Park estate near Minneapolis on 21 April. Fentanyl is a synthetic opioid, 50 times more potent than heroin, that has been partly responsible for a recent surge in overdose deaths in some parts of the US. It also has legitimate medical uses.

The findings confirm suspicions that opioids played a role in the star's death. Afterwards authorities began reviewing whether an overdose was to blame and whether he had been prescribed drugs in the preceding weeks. His death came less than a week after his plane made an emergency stop in Illinois so he could undergo medical treatment. Prince was found on the jet as he was returning from a concert in Atlanta. First responders gave him a shot of Narcan, an antidote. used in suspected opioid overdoses. At least two doctors' names have come up in the investigation into the death by the Carver County Sheriff's Office, the US Attorney's Office in Minnesota and the Drug Enforcement Administration.

Dr Michael Todd Schulenberg, a family practitioner, treated Prince twice in the weeks before his death and told investigators he prescribed medications for the singer. The medications were not specified in a search warrant for the Minnesota hospital that employed Dr Schulenberg at the time. Dr Schulenberg saw Prince on 7 April and 20 April - the day before his death - according to the warrant. The doctor's lawyer has declined to comment on the case. Dr Howard Kornfeld, a California addiction specialist, was asked by Prince's representatives on 20 April to help the singer. He sent his son Andrew on a flight that night. Andrew was among the people who found Prince's unresponsive body the next morning, according to Dr Kornfeld's lawyer, William Mauzy.

The younger Kornfeld, who is not a doctor, was carrying buprenorphine, a medication that can be used to treat opioid addiction. The medication eases cravings and withdrawal symptoms, Mr Mauzy said. Mr Mauzy explained that Andrew Kornfeld intended to give the medication to a Minnesota doctor who was seeing Prince on 21 April. Mr Mauzy has refused to identify that doctor. Dr Schulenberg is not authorised to prescribe buprenorphine. Prince's death came two weeks after he cancelled concerts in Atlanta, saying he wasn't feeling well. The superstar had a reputation for clean living, and some friends said they never saw any sign of drug use. But longtime friend and collaborator Sheila E has told the Associated Press that Prince had physical issues from performing. She cited hip and knee problems that she said came from years of jumping off risers and stage speakers in heels.