Detectives have questioned George Michael's lover Fadi Fawaz as it emerged that a major crimes unit has taken over the inquiry amid fears he died of a drugs overdose.
Michael, 53, passed away in his bed at home in Goring-on-Thames, Oxfordshire on Christmas Day, apparently from heart failure.
Mr Fawaz has now been interviewed by police about what he knows about Michael's final hours, according to the Daily Mirror.
The investigation has been taken over by the Thames Valley Police Major Crime Unit, the Sun reported.
Last week a post-mortem examination proved "inconclusive" but the results of toxicology tests could shed new light on the star's death, which is currently classed as "non-suspicious".
Detectives fear he may have been killed by a drugs overdose.
Mr Fawaz, 40, who lives near London's Regent's Park, was questioned this week by police.
Police officers are compiling a report for the Oxfordshire coroner, Darren Salter, who will hold an inquest later this year.
The Sun claimed detectives had asked a paparazzi agency to hand over the pictures it took showing who was coming and going from the star's house before he died.
Mr Fawaz, who found Michael's body, claimed recently his Twitter page had been hacked after tweets were posted claiming the singer had "tried to kill himself many times".
Last week the Australian-born hair stylist told the Daily Mirror he fell asleep in his car on Christmas Eve and added: "I never saw him that night. The police know everything. That's the most important thing.:
Mr Fawaz was photographed in the street this week and appeared appeared to be feeling the strain from the past two weeks.
In a statement about Michael's death, Mr Fawaz - who had been in a relationship with Michael since 2009 - spoke about how excited they had been to share Christmas together.
He said: "We were supposed to be going for Christmas lunch. I went round there to wake him up and he was just gone, lying peacefully in bed.
"We don't know what happened yet. Everything had been very complicated recently, but George was looking forward to Christmas, and so was I."
Mr Fawaz later tweeted that he would "never stop missing" the star.
Days later, he posted a poignant link to one of star's "lost" songs online, but had to take it down amid a legal row over property rights.
The song, This Kind of Love, was from the Wham! star's unreleased album Trojan Souls.
The song includes the touching lyrics: "Now everyone has to get over I know. But this empty house seems to get colder and colder. So won't you stay here with me?
"Now that I found you. I can't let you go."
But Mr Fawaz later removed the link as lawyers for Michael's estate attempt to have the song wiped from the internet, citing intellectual property rights.
Then, on New Year's Day, posts on Mr Fawaz's Twitter account claimed the singer had 'tried numbers of time to kill himself many times' and had "finally managed".
They read: "The only thing George wanted is to DIE. He tried numbers of time to kill himself many times..
"And finally he managed...
"We loved each other very much and we were together almost 24 hours a day..."(sic)
Mr Fawaz later denied writing the tweets, saying the account had been hacked.
He said: "I am shocked with what's going on with the Twitter thing. It's a bit scary to be honest. I did not send those tweets."