Prescription drugs were discovered with Prince when he was found dead in his home, according to media reports.
Citing law enforcement sources, ABC, NBC, CBS and CNN reported that prescription painkillers were found on the 57-year-old and in his Paisley Park home in Minneapolis.
The Star Tribune, also citing unnamed sources, reported that prescription pills were found but that it was not clear whether they had been prescribed to Prince.
Prince died on April 21, and an autopsy has been performed but results are not expected for three to four weeks.
The star's death came less than a week after reports that his plane made an emergency landing in Moline, Illinois, as he returned after performing in Atlanta.
TMZ reported that Prince was treated for an overdose of the painkiller Percocet.
Airport and public safety officials in Moline have refused to confirm that the plane that made an emergency landing in Moline was Prince's aircraft, and heavily redacted incident reports did not identify the person who was treated.
Carver County Deputy Sheriff Jason Kamerud declined to comment on the reports of drugs found at Paisley Park.
He said he strongly disputed reports by several media outlets that investigators had asked the US Drug Enforcement Administration for help in the case.
Mr Kamerud said: "We have not asked them for help, or asked them to be a part of the investigation.
"We might contact them to help us, but that hasn't happened. We don't have the medical examiner's report yet. We don't know to what extent pharmaceuticals could be a part of this."
Long-time friend and collaborator Sheila E said Prince had physical issues from performing, citing hip and knee problems that she said came from years of jumping off risers and stage speakers in heels.