Prince’s cause of death has been confirmed to be opioid overdose, reports the Associated Press.

A law enforcement official working the case says that tests showed Prince passed away after overdosing on drugs. The official spoke on condition of anonymity, as he was not cleared to speak about the case publicly.

A press release from the Midwest Medical Examiner’s Office notes that Prince overdosed on fentanyl, a powerful synthetic painkiller similar to morphine.

Shortly after Prince died on April 21 at his estate in Minneapolis, reports rolled in stating that he had been abusing Percocet and was seeking medical help for his addiction.

Investigators have been reviewing whether a doctor legally prescribed Prince the drugs that led to his death at the age of 57.