Whitney Houston could be the latest celebrity whose cause of death was prescription drugs.

Police discovered a half dozen pill bottles in Houston's room at the Beverly Hills Hilton, TMZ reported, adding that family members said Houston had been taking Xanax, a drug often used to treat anxiety.

When combined with alcohol, Xanax is known to cause drowsiness. A member of Houston's entourage found her in a bathtub around 3:30 p.m. Saturday. TMZ said her head was under water and she could not be resuscitated by paramedics after being removed from the tub.

At 3:55 p.m., Whitney Houston was pronounced dead at the Beverly Hilton Hotel, Beverly Hills police spokesman Lt. Mark Rosen told reporters at a press conference, adding that the cause of death was still being investigated.

Sources told E! News that Houston had had prescriptions for antidepression and antianxiety medication for years. Houston reportedly believed Xanax helped calm her nerves before going out in public.

There are multiple reports that Houston had been drinking with friends the night before her death at the hotel, though no alcohol was found in the preliminary sweep of Houston's room, TMZ reported.

The troubled superstar attended rehearsals for the Grammys on Thursday, coaching singers Brandy and Monica, Fox News reported, citing a person who was at the event. That person, who spoke on the condition of anonymity, said Houston looked disheveled, was sweating profusely, and liquor and cigarettes could be smelled on her breath.

Multiple reports say Houston was observed behaving erratically earlier in the week at a Los Angeles club.

The 48-year-old singer's body was removed from the hotel Sunday morning and taken to the Los Angeles County coroner's office where an autopsy will be performed to determine the cause of death.

The official cause of death could be delayed by up to six weeks pending toxicology tests. However, Beverly Hills police issued a statement saying, There were no obvious signs of criminal intent.

Houston was at the hotel preparing to attend Clive Davis' annual pre-Grammy gala.

A longtime producer and mentor of Houston, Davis announced before the party that he was personally devastated by the loss of somebody who meant so much to me. Whitney was so full of life. She was so looking forward to tonight ... she loved music. She loved this night. Let's celebrate music.

Davis called Houston a beautiful person and said the six-time Grammy winner had talent beyond compare.

She graced this stage with her regal presence so many times, he added. Simply put, Whitney would have wanted the music to go on and her family asked us to carry on.

There were no immediate words on funeral plans, though Houston's childhood church in Newark, N.J., Hope Baptist Church, held a special service for her Sunday morning.

Born into greatness -- the daughter of gospel singer Cissy Houston, cousin of 1960s pop diva Dionne Warwick, and goddaughter of Aretha Franklin -- Houston began singing in church as a child. In her teens, she sang backup for Chaka Khan, Jermaine Jackson and others, in addition to modeling.

From the mid-1980s to the late 1990s, she was one of the world's best selling artists, dabbling in acting with films like The Bodyguard and Waiting to Exhale.

Houston ruled as pop music's queen until her majestic voice and regal image was tainted by drug use, erratic behavior, and a tumultuous marriage to singer Bobby Brown.

Houston had drug and alcohol problems for several years and last May her spokeswoman said she was going back into rehab.

The biggest devil is me. Houston told ABC's Diane Sawyer in an infamous 2002 interview with then-husband Brown by her side. I'm either my best friend or my worst enemy.