Police are investigating whether foul play was involved in Prince's death after authorities revealed there was "no reason to believe" he killed himself.
The music superstar died at his Paisley Park estate near Minneapolis on Thursday after he was found collapsed in a lift. He was 57.
Carver County Sheriff Jim Olson said there were "no obvious signs of trauma" on Prince's body and it was "still under investigation" whether foul play was involved.
Speaking at a press conference at Carver County Courthouse in Chaska, Minnesota, Sheriff Olson refused to comment on reports that Prince had been taking a powerful painkiller before his death.
He said Prince was last seen at 8pm the night before his death when he was dropped off at Paisley Park.
The singer had been alone at the estate and staff members had been unable to reach him, the official added.
A post-mortem examination took place on Friday, where information about Prince's "medical and social history" was gathered, the Midwest Medical Examiner's Office said.
His body has been released to his family but a cause of death may not be made public for weeks, officials said.
Celebrity news website TMZ reported that Prince had overdosed on a painkiller called Percocet when his private jet made an emergency landing in Atlanta, Georgia, on April 15, six days before his death.
The star was taking the drug for a hip problem after having corrective surgery around six years ago, TMZ said.
A spokeswoman for the Midwest Medical Examiner's Office said it would not release information from the post-mortem examination until "all results are obtained" and the findings of a toxicology scan "could likely take weeks".