The official, speaking on condition of anonymity, confirmed to the Associated Press that investigators are also looking into whether a doctor was on a plane that made an emergency landing in Illinois less than a week before Prince died.
The official also said investigators are looking into what kinds of drugs were on the plane and at Prince's house in suburban Minneapolis.
The official also confirmed some details that have previously been reported by other media outlets, including TMZ.
Prince's plane made an emergency stop in Moline, in western Illinois, on April 15 and he was found unconscious on the plane, the official said.
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The person said first responders gave Prince a shot of Narcan, which is used in suspected opioid overdoses.
The official said the shot was given when the plane was on the runway in Moline as Prince returned to Minneapolis following a performance in Atlanta.
The official said investigators are looking at whether Prince overdosed on the plane and whether an overdose killed him, and at what kind of drugs were involved. One possibility is the powerful painkiller Percocet or something similar, the official said.
Narcan can be used on people even if an overdose isn't confirmed because it wouldn't necessarily be harmful.
A second law enforcement official, also on condition of anonymity, told AP that prescription drugs were discovered at Prince's home when the musician was found dead on April 21.
An autopsy has been performed, but results aren't expected for three to four weeks.
The search warrant for Prince's Paisley Park home and studio - carried out the day of his death - was filed Thursday under seal at the request of investigators who said it would hamper their investigation if contents were public.
The filing, signed by Carver County Chief Deputy Jason Kamerud, also warned that disclosing details in the warrant could cause "the search or related searches to be unsuccessful" and risk injury to innocent people.
Prince's death came two weeks after he cancelled concerts in Atlanta, saying he wasn't feeling well.