The toxicology reports for Prince Rogers Nelson have finally come back from the Midwest Medical Examiner’s Office, and they have determined he died from an accidental overdose of the opioid Fentanyl.

On April 21, Prince was found unresponsive in an elevator at his Paisley Park home and recording studio in Chanhassen, Minnesota. Sheriff’s deputies tried administering CPR, but failed to revive the singer. At the age of 57, Prince was was pronounced dead at 10:07 a.m.

Prince’s death has been deemed accidental, caused by “self-administerd fentanyl.” There’s no word yet on if he was prescribed the drug. An investigation is ongoing to determine how the prescription drug was obtained by the singer.

Fentanyl is reportedly prescribed by doctors to treat cancer patients, and is being blamed for the rise in overdose deaths in the U.S., said CNN.

It's 25 to 50 times more potent than heroin and 50 to 100 times more potent than morphine, according to the U.S. Drug Enforcement Administration.