Los Angeles: Late pop icon Prince died from an accidental overdose of the painkiller fentanyl, medical examiners have found. The report, from the Midwest Medical Examiner's Office in Minnesota, comes more than a month after the singer was found slumped in a lift at his home. According to the autopsy report, Prince self-administered fentanyl, an opioid many times more powerful than heroin, the BBC reported. Detectives have already questioned a doctor who saw the 57-year-old twice in the weeks before he died. Prescription painkillers were in the singer's possession following his death, officials revealed in May. A police warrant has also revealed that the doctor, Michael Schulenberg, prescribed medication to the singer on 20 April -- the day before he died. The warrant does not say what was prescribed or whether Prince took the drugs. In March last year, the US Drug and Enforcement Administration (DEA) warned the drug, which it said was often laced with heroin, was a "threat to health and public safety". It said even small doses of fentanyl could be lethal and that "incidents" and overdoses related to the drug were "occurring at an alarming rate". Prince was found unresponsive in a lift at his Paisley Park Studios on the morning of April 21, local officials said. First responders tried to revive him with cardiopulmonary resuscitation (CPR) but he was pronounced dead shortly afterwards.