There is "no reason to believe" that Prince's death was suicide, the sheriff of the Minnesota county where the singer had his home has said after a post-mortem examination.

There was no sign of trauma on the body, Sheriff Jim Olson said, suggesting the singer had died alone.

Prince, 57, was found dead in a lift on his Paisley Park estate on Thursday.

Fans have been wearing purple, the colour associated with the musician who sold more than 100m records.

His innovative music spanned rock, funk and jazz. He was at his peak in the 1980s with albums like Dirty Mind, 1999 and Sign O' The Times.

The sheriff warned that full results from the post-mortem could take several weeks, and the incident was still under investigation.

Olson said it was not unusual for there to be no one in the residence except Prince.

The singer was last seen at about 20:00 on Wednesday night (01:00 GMT on Thursday) and was found unconscious by some of his staff at about 09:30 the next morning.

Prince had been rushed to hospital in Illinois six days earlier, while flying home from a concert in Georgia, but was treated and released a few hours later.

Quoting unnamed sources, US entertainment news site TMZ reports that Prince was treated in Illinois for an overdose of the painkiller drug Percocet.

Declining to give details of the preliminary findings, medical examiner spokesperson Martha Weaver said a full set of tests would be done on the body, involving tissue and blood samples.

Earlier, she announced that the body would be released to the family on Friday.

Sheriff Olson confirmed police were in contact with Prince's family.

"We have no reason to believe at this point that this was a suicide," he said, then added, "but again, this is early on in the investigation and we're continuing to investigate."

He spoke of Prince as a good member of the community and said he had been a "friend to [his staff] as well as being an employer".

Fans have set up impromptu memorials in his home town Minneapolis and in New York.

In London, US President Barack Obama said he and the US ambassador began the day by listening to Prince's hit Purple Rain and Delirious before attending bilateral meetings.

Prince had spoken about struggling with childhood epilepsy, the Associated Press reports, and friends say he had hip trouble.

His former percussionist, Sheila E, told the news agency Prince had suffered the effects of years of jumping off risers and speakers on stage while wearing high heels.

"There was always something kind of bothering him, as it does all of us," she said. "I hurt every single day. You know we're like athletes, we train, and we get hurt all the time. We have so many injuries."

Born Prince Rogers Nelson in 1958, he was a prolific writer and performer from a young age - reportedly writing his first song when he was seven.

He was also an arranger and multi-instrumentalist, and recorded more than 30 albums. Hits included Let's Go Crazy and When Doves Cry.

In 1984, he won an Oscar for the score to Purple Rain, a film in which he also starred.

Throughout his career he had a reputation for secrecy and eccentricity, once changing his name to an unpronounceable symbol.

He had a mercurial relationship with technology. In 2000, he released singles via the pioneering music-sharing service Napster, but he later declared the internet "completely over" and refused to allow his music on major streaming platforms.

Prince's latest album, HITnRUN Phase Two, was released last year and he had been touring as recently as last week.