Medical examiners said Friday they had completed a four-hour autopsy of pop superstar Prince, who died Thursday at 57 in his estate outside of Minneapolis, Minnesota.

Gathering the findings of the examination will take several days, and the results of a full toxicology scan - which could show any toxic substances or drugs in Prince's body - could take weeks, the Midwest Medical Examiners Office said.

Investigators will collect "relevant information" about the musician's medical and family history to determine what caused his death.

"Anything which could be relevant to the examination will be taken into consideration," the office said.

Carver County Sheriff Jim Olsen said he would summarize public information about the ongoing investigation at a press conference at 3 pm (2000 GMT).

Prince, 57, had reportedly been ill and had postponed two concerts in Atlanta for a week because of what his representatives said was the flu.

His private plane had landed midway through his flight home from the rescheduled shows in Atlanta on April 15 for a medical emergency.

But witnesses said he had appeared healthy the next day in a brief appearance at a dance party at his Paisley Park compound.

Medics on Thursday morning responded to an emergency call that Prince had been found unconscious in an elevator, but were unable to revive him. He was declared dead a short time later.

Public mourning for the flamboyant pop genius continued Friday after overnight tributes drew thousands of fans in New York, Los Angeles, San Francisco, New Orleans, Boston and Prince's hometown of Minneapolis.

US President Barack Obama said he "warmed up" for bilateral talks in London by listening to Prince's song's Delirious and Purple Rain on a turntable at the US ambassador's residence.

He told press, "I love Prince" and called his death "a remarkable loss."

Born Prince Rogers Nelson, Prince released more than three dozen studio albums over his 35-year career. He won seven Grammys and an Academy Award, and was inducted to the Rock and Roll Hall of Fame in 2004.

Prince is one of the best-selling recording artists of all time. He charted more than 50 worldwide top 40 hits, according to the Los Angeles Times, including Little Red Corvette, 1999, Raspberry Beret, When Doves Cry and I Would Die 4 U.

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