The Associated Press has obtained a "confidential" autopsy and toxicology report that essentially more than confirms earlier findings that Prince died of a fentanyl overdose in April 2016. According to Billboard, the report shows that he had 67.8 micrograms of fentanyl per liter of blood in his system at the time of his death. Dr. Lewis Nelson, chairman of emergency medicine at Rutgers New Jersey Medical School, told the AP that "The amount in [Prince's] blood is exceedingly high, even for somebody who is a chronic pain patient on fentanyl patches."
It's worth it to note, as the AP does, that there's apparently no fixed "lethal level" of fentanyl, as deaths have occurred in people with anywhere between three to 58 micrograms of the opiate in their blood. The report also says that Prince had concentrations of fentanyl in his liver and stomach, which suggests he was taking the drug orally.
Fentanyl is also suspected as being responsible for the death of rapper Lil Peep in November 2017, along with a Xanax overdose. The drug is furthermore at the centre of an ongoing opioid crisis in Canada. Read more about Prince's toxicology report here.