US singer Prince died of an opioid overdose, sources have told Associated Press and a Minnesota website.
A law enforcement official, who is close to the investigation, told AP this was established by tests after the singer’s death in April in Minneapolis.
Detectives have already questioned a doctor who saw the 57-year-old twice in the weeks before he died.
Prescription painkillers were in the singer’s possession following his death, officials told US media in May.
A police warrant has also revealed that Dr Michael Schulenberg prescribed medication to the singer on 20 April – the day before he died.
The warrant does not say what was prescribed or whether Prince took the drugs.
AP says the law enforcement official spoke on condition of anonymity on Thursday because he was not authorised to speak to the media.
Separately, the Star Tribune in Minnesota quoted a source with knowledge of Prince’s death investigation as saying he died from an overdose of painkillers.
Officials in Minneapolis said after a post-mortem examination that there had been no reason to believe that Prince’s death was suicide.
Prince was found unresponsive in a lift at his Paisley Park Studios on the morning of 21 April, local officials said. First responders tried to revive him with CPR but he was pronounced dead shortly afterwards.
Artists from around the world and Prince’s numerous fans later paid tributes to the star.
Prince was cremated in a private ceremony on 24 April. The singer’s family are understood to be planning to stage a public memorial in August.
He was a prolific writer and performer from a young age, reportedly writing his first song when he was seven.
A singer, songwriter, arranger and multi-instrumentalist, Prince recorded more than 30 albums. His best known hits include Let’s Go Crazy and When Doves Cry.