The official spoke with The AP on the condition of anonymity because he's not permitted to speak to the media, ABC News reported.
KSTP is reporting that multiple sources claim fentanyl was found in his system.
The Midwest Medical Examiner's Office also released the autopsy results.
The results confirm that Prince self -administered fentanyl and died of fentanyl toxicity, ruling his death an accident.
The singer was found dead in his Paisley Park home in Chanhassen, Minnesota, in April.
He was 57.
His dead was a week after a private plane made an emergency landing in Illinois, CNN reported.
Officials said Prince was found unconscious on the plane and was given Narcan by first responders, ABC News reported. Narcan is used in suspected opioid overdoses.
Prince had been cremated just days after his death.