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."