Prince's long-time lawyer has called his death a complete shock and disputed suggestions the singer had a drug addiction.

Prince was found dead in Paisley Park, his home and vast recording studio in Chanhassen, Minnesota, on Thursday at the age of 57.

A post-mortem was conducted, but complete results will not be in for weeks. Police have said there was no indication of suicide.

Lawyer L Londell McMillan had known Prince for 25 years and at one time was his manager.

He told The Associated Press he spoke to Prince the Sunday before he died, after it was reported that his plane made an emergency landing to deal with a medical emergency involving the singer.

Prince assured Mr McMillan he was fine.

"He said he was doing perfect," Mr McMillan recalled. "He said, 'Okay, I'll call you soon.'"

Celebrity website TMZ reported that Prince was treated for an overdose of a powerful painkiller while travelling home from concerts in Atlanta last week.

The site reported that Prince's plane made an emergency landing on April 15 in Moline, Illinois, where he was briefly admitted to hospital.

Prince had postponed concerts in Atlanta citing an illness but rescheduled them and performed there on April 14.

Asked about the TMZ report, Mr McMillan said that while Prince may have been in pain and may have taken medication from time to time, he was "not on any drugs that would be any cause for concern".

"People use medication. The question is, are you on meds in a dangerous way?" he said.

Mr McMillan noted that Prince, a vegan, was known for his clean lifestyle.

"Everybody who knows Prince knows he wasn't walking around drugged up," Mr McMillan said. "That's foolish. No one ever saw Prince and said 'He looks high'. It wasn't what he was about."

Mr McMillan also said Prince was in great spirits.

"Prince had an amazing life. He enjoyed life," he said. "He had a lot of fun."

Mr McMillan, whose clients also included Michael Jackson, said he owed his career to Prince. He managed the star amid Prince's battles with his label, Warner Bros Records. Prince credited him with coming up with the title The Artist when he stopped using his name and took on a symbol instead as part of that battle.

"I'm shocked and overwhelmed," Mr McMillan said of Prince's death.

He was among those present for a private and intimate memorial service at Paisley Park on Saturday. Prince was cremated.

"It was a very loving and special, solemn and very appreciative," Mr McMillan said. "I think he would have been proud of how we celebrated his life."