Whitney Houston's autopsy has been officially completed, but results will be kept private.

The iconic singer was pronounced dead in a fourth-floor hotel room last Saturday afternoon, with no immediate apparent cause of death.

US website TMZ reported that prescription drugs were found in the star's room and there is speculation that Whitney may have drowned in her bathtub while heavily sedated.

A post-mortem examination was performed on the star by the Los Angeles County Coroner's Office on Sunday.

Although Beverly Hills Police Department's Lt Mark Rosen revealed that there were "no obvious signs of criminal intent" involved with Whitney's demise, authorities have decided to put a security hold on the case. Investigators do not want the release of information to impede their inquiry.

TMZ reports that according to law enforcement sources medical examiners found that Whitney had water on her lungs when she died. These officials need to know the precise amount of water in the organs before they can determine her exact cause of death.

Toxicology reports won't be available for another six to eight weeks. Authorities are planning to reveal their official findings after the results are received.

Whitney's family is struggling with her shocking death. Bobbi Kristina, Whitney's 18-year-old daughter with singer Bobby Brown, was taken to hospital and subsequently released for "stress and anxiety" yesterday.

"Today my daughter did visit with doctors at Cedars-Sinai Medical Center in Los Angeles. She has been released and is presently with my family, including her siblings," Bobby said in a statement released to Extra yesterday. "Obviously the death of her mother is affecting her, however, we will get through this tragedy as a family. Again, I ask for privacy during this time."

Whitney, a six-time Grammy Award-winning artist, was given a grand tribute at the 54th Annual Grammy Awards Sunday. Numerous artists including Jennifer Hudson and Grammys host LL Cool J honoured the contribution she has made to music and expressed their lamentation over her passing.