Police received 47 calls from Prince's Paisley Park residence over the past five years, with three in the past nine months alone for unspecified medical emergencies, the last of which was on his death.

A police report containing details of the response to his death including how emergency services battled to save him has now been released, with officers indicating they have launched a "criminal" probe.

The 57-year-old superstar was found "unresponsive" in an elevator at his $10 million Paisley Park estate in Minnesota last Thursday.

Documents have now confirmed details about the incident and show the singer was pronounced dead less than 20 minutes after an ambulance arrived on the scene shortly before 9.50am.

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Jason Kamerud, chief deputy of Carver County Sheriff's Office, wrote: "On 4/21/2016 at about 0943 hours, sheriff's deputies were dispatched to a medical call at Paisley Park.

"Sheriff's deputies and emergency personnel from Chanhassen Fire and Ridgeview Ambulance arrived at about 0948 hours and found an unresponsive adult male in the elevator.

"They tried to provide lifesaving CPR, but were unable to revive the victim. He was pronounced deceased at 1007 hours."

It came as the sheriff's office suggested they were not going to issue any more information on the singer's death because details about cases of a "criminal" nature can be withheld.

According to the Star Tribune, police said: "Investigative data collected or created by a law enforcement agency in order to prepare a case against a person, whether known or unknown, for the commission of a crime or other offence for which the agency has primary investigative responsibility are confidential or protected non-public while the investigation is active."

The statement suggests charges could be brought against a person in relation to the death. It is not yet known what these could be.

Sources claimed officers may be looking into whether Prince overdosed on opioids.

They are also considering whether a doctor was prescribing him drugs in the weeks before he was found dead, a law enforcement official claimed.

The official said that among the things investigators are looking at is whether a doctor was with Prince on a plane that made an emergency landing in Illinois less than a week before the star died.

It comes after a search warrant was granted by a judge for the singer's house after claims he had prescription painkillers on him when he died.

The warrant is for the musician's home and recording studio complex. The local sheriff and prosecutor filed papers on Thursday requesting that the warrant be sealed for six months.

Officers have already revealed they found no signs of suicide or obvious trauma while probing the death.

They also admitted it could take weeks before autopsy results reveal how the star died.

- Daily Mail