Prescription drugs were found in Prince's possession when he died, according to US reports.
Officials told NBC News the painkillers were discovered in his Minneapolis home - but it is as yet unclear if they played any part in his death.
The pop star died aged 57 on April 21 after being found collapsed in a lift at his Paisley Park estate.
The emergency dispatch call made in the moments surrounding Prince's death have emerged after being obtained by showbiz site TMZ.
In the audio release an operator can be heard saying there is a "male down, not breathing" at the singer's address.
The painkillers were reportedly found in the singer's possession when he died - but it is unclear if they played any part in his death.
Mourners celebrate pop icon at private memorial at Paisley Park estate.
Star's ex-manager voiced concerns over whether whoever inherits the star's fortune, and valuable catalogue of works, will know what to do.