A toxicology report from Prince’s autopsy shows he had exceedingly high concentrations of fentanyl throughout his body when he died.

Prince was 57 when he was found alone and unresponsive in an elevator at his Paisley Park estate on April 21, 2016. Public data released six weeks later showed he died of an accidental fentanyl overdose.

A confidential toxicology report obtained Monday by The Associated Press says the concentration of fentanyl in Prince’s blood was 67.8 migrograms per liter – a level experts called exceedingly high, even for someone who may have a tolerance to opioids.

The level of fentanyl in Prince’s liver was 450 micrograms per kilogram. The report explains that liver concentrations greater than 69 micrograms per kilogram “seem to represent overdose or fatal toxicity cases.” There was also what experts called a potentially lethal amount of fentanyl in his stomach, which his body had not absorbed.