The cause of Prince's death may not be made public for weeks, officials said, as it was reported that the pop superstar overdosed on a powerful painkiller six days before he died.
The American musician was pronounced dead at his Paisley Park estate near Minneapolis on Thursday, with tributes pouring in from the world of music and beyond.
A post-mortem examination was taking place on the 57-year-old's body on Friday, where information about his "medical and social history" was gathered, the Midwest Medical Examiner's Office 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.
The Purple Rain 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".
Carver County Sheriff's office said a press conference would take place later to provide an update on the investigation into Prince's death.
A day after Prince was rushed to hospital on April 15, he hosted a dance party at Paisley Park where fans said he "seemed happy" and appeared to look healthy.
Gretchen Richardson, 27, told the Press Association: "It was just a short appearance. He just said, 'Save your prayers for a couple of days. I'm OK. I'm here, thank you. I appreciate it'."
Jeremiah Freed, who also attended the event, said that Prince told the crowd: "Just wait a few days before saying your prayers."
Tributes have flooded in for the singer, whose full name was Prince Rogers Nelson. US president Barack Obama described Prince as a "creative icon".
Madonna said he was a "true visionary" while Sir Elton John shared a picture of Prince on his Instagram page, writing: "The greatest performer I have ever seen."
Sales of Prince's music soared after news broke of the pop star's death, and fans continued to leave floral tributes at Paisley Park many hours after his death was announced.
Thousands of Prince fans also gathered at the club in Minneapolis where he filmed Purple Rain as the venue hosted a free all-night dance party in his honour. Two more similar events are planned at the venue over the weekend.