Prince died of an overdose of fentanyl, a powerful opioid painkiller that is up to 50 times more potent than heroin, autopsy results released Thursday show.The findings confirm suspicions that opioids played a role in the death of the superstar musician, who was found dead April 21 at his Minneapolis-area estate, said AP.It was not immediately clear whether Prince had a prescription for the drug and, if not, how he obtained it.At least one friend has said he suffered from intense knee and hip pain from many years of stage performances.The results raised the possibility that anyone who provided the drug illegally could face criminal charges.Although the death was formally ruled an accident, that merely signified that it was not intentional and in no way precludes prosecution.After Prince died, authorities began reviewing whether an overdose was to blame and whether he had been prescribed drugs in the preceding weeks.According to a one-page report released by the Midwest Medical Examiner’s Office, Prince administered the drug himself on an unknown date.The office said the death investigation is complete, and it had no further comment.Confirmation that Prince died of an opioid overdose was first reported by The Associated Press. The autopsy report was released hours later.Fentanyl is a synthetic drug that has legitimate medical uses. It is also partly responsible for a recent surge in overdose deaths in some parts of the country.Because of its risks, it is tightly controlled by the Food and Drug Administration, but much of it is manufactured illegally.Prince, 57, died less than a week after his plane made an emergency stop in Moline, Illinois, for medical treatment as he was returning from an Atlanta concert.The Associated Press and other media reported, based on anonymous sources, that he was found unconscious on the plane, and first responders gave him a shot of Narcan, an antidote used in suspected opioid overdoses.The autopsy was conducted the day after Prince’s body was found. When his body was examined, he was 5 feet 3 inches tall, weighed 112 pounds and was dressed almost entirely in black.He had scars on his left hip and right lower leg. The report did not say whether those scars were evidence of any past surgery to relieve pain.