Prince died from an overdose of painkillers, a source with knowledge of the megastar’s death investigation has told the Star Tribune.

The 57-year-old musician was pronounced dead the morning of April 21, one day before he was scheduled to meet with a California doctor in an attempt to kick an opioid addiction.

Two of his staff members — longtime friend Kirk Johnson and personal assistant Meron Bekure — found his lifeless body in a Paisley Park elevator about 9:40 a.m.

While the official autopsy and toxicology results have yet to be publicly reported, sources have told the Star Tribune that the investigation has focused on Prince’s use of painkillers and how he obtained them.

The Associated Press in Chicago, citing an unidentified law enforcement official, also reported Thursday that Prince died from an opioid overdose.

The day before his death, Prince was treated by a local doctor for withdrawal symptoms from opioid addiction. The physician, Dr. Michael Todd Schulenberg, a family practitioner, treated Prince for fatigue, anemia and concerns about opiate withdrawal.

Schulenberg, however, did not prescribe opioids to Prince, a source has said.

Prince died less than a week after his private plane made an emergency, middle-of-the-night landing in Moline, so he could be treated for a suspected opioid overdose following a pair of concert performances in Atlanta, sources told the Star Tribune.

Emergency responders arrived at the Chanhassen complex the morning of April 21 within five minutes of receiving a 911 call, but it was already too late. A responding paramedic told staff members, law enforcement officers and others at the scene that Prince appeared to have been dead for at least six hours by the time his body was found.

Sources have told the Star Tribune that Prince’s inner circle became so concerned about his health that they reached out to Phaedra Ellis-Lamkins, a well-known environmental and labor activist in the San Francisco Bay Area who has been credited with helping Prince recover the rights to his early catalog of songs from Warner Bros. She has declined to comment, citing Prince’s concern for his privacy.

The night of April 20, less than 12 hours before Prince’s body was found, Ellis-Lamkins called Dr. Howard Kornfeld, a pain and addiction specialist in Mill Valley, Calif., seeking his help to get the musician off prescription painkillers, sources said.

Kornfeld could not clear his schedule to immediately travel to Minnesota, so he instead dispatched his son, Andrew Kornfeld, a pre-med student who worked with his father, to meet with Prince and a second Minnesota doctor who is certified to prescribe an opioid addiction treatment medication that Dr. Kornfeld uses.

That Minnesota doctor, who hasn’t been publicly identified, had cleared his calendar for the morning of April 21 so that Prince could go to his office for an independent evaluation, the source said.

Prince died before the meeting could take place.

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