Late singer George Michael's boyfriend Fadi Fawaz will be questioned again by detectives as they fear the singer may have died from a drug overdose on Christmas 2016.

Michael's sudden death is still being treated as "non-suspicious", but a crime unit from Thames Valley Police who specialise in murders and rapes, has now been brought on board, reports femalefirst.co.uk.

The officials are reportedly planning to grill Fawaz, who dated the singer from 2012 until his death, once again this week, as well as Michael's housekeeper and neighbours.

"The investigation is now picking up a bit of speed. Officers from the Major Crime Unit have begun asking questions of those who were in the area at the time George died and the day before. They want to build up an idea of what George's last seven days were like and who came and went," a source told The Sun newspaper.

It was initially claimed the "Careless whisper" hitmaker, who was found dead at the age of 53, died from heart failure. But it is now thought the singer, who had an estimated fortune of 105 million pounds, passed away from an overdose of illegal or prescription drugs.

A post-mortem was carried out last week on Michael's body, but the cause of death could not be detected. Now toxicology tests are underway to determine what led to his death.