LOS ANGELES — Six-time Grammy Award winner Whitney Houston, who ruled as pop music's queen until her majestic voice and regal image were ravaged by drug use, erratic behavior and a tumultuous marriage to singer Bobby Brown, has died. She was 48.

Beverly Hills police Lt. Mark Rosen said outside the Beverly Hilton that Miss Houston was pronounced dead at 3:55 p.m. Saturday in her room. Detectives were investigating the death.

Miss Houston's publicist, Kristen Foster, said the cause of death was unknown.

News of the singer's death came on the eve of music's biggest night: the Grammy Awards, where she once reigned, and her death was sure to cast a heavy pall on Sunday's ceremony.

Miss Houston was supposed to attend mentor Clive Davis' pre-Grammy gala concert and dinner Saturday, and had been at rehearsals for the show Thursday, according to a person who was at the event. The person said she looked disheveled, was sweating profusely and liquor and cigarettes could be smelled on her breath.

At her peak, Miss Houston was the golden girl of the music industry. From the middle 1980s to the late 1990s, she was one of the world's best-selling artists, with more than 55 million records sold in the United States alone.

She wowed audiences with effortless, powerful and peerless vocals that were rooted in the black church but made palatable to the masses with a pop sheen.

Her success carried her beyond music to movies, where she starred in hits such as "The Bodyguard" and "Waiting to Exhale."

She had the perfect voice, and the perfect image: a gorgeous singer who had sex appeal but was never overtly sexual, who maintained perfect poise.

By the end of her career, Miss Houston had become a stunning cautionary tale of the toll of drug use. Her album sales plummeted and the hits stopped; her image was shattered by a wild demeanor and bizarre public appearances. She confessed to abusing cocaine, marijuana and pills, and her voice became raspy and hoarse, unable to hit the high notes as she had during her prime.

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

She seemed to be born into greatness. She was the daughter of gospel singer Cissy Houston, the cousin of 1960s pop diva Dionne Warwick and the goddaughter of Aretha Franklin.

Miss Houston started singing as a child at church. In her teens, she sang backup for Chaka Khan, Jermaine Jackson and others, in addition to modeling.

She made her album debut in 1985 with "Whitney Houston," which sold millions and spawned hit after hit. "Saving All My Love for You" brought her her first Grammy, for best female pop vocal. "How Will I Know," "You Give Good Love" and "The Greatest Love of All" also became hit singles.

Another multiplatinum album, "Whitney," came out in 1987 and included hits such as "Where Do Broken Hearts Go" and "I Wanna Dance With Somebody."

The New York Times wrote that she "possesses one of her generation's most powerful gospel-trained voices, but she eschews many of the churchier mannerisms of her forerunners."

Some saw her 1992 marriage to former New Edition member and soul crooner Brown as an attempt to refute critics who accused her of playing down her black roots to cultivate white audiences. It seemed to be an odd union; she was seen as pop's pure princess while he had a bad-boy image. The couple had one daughter, Bobbi Kristina, in 1993. Over the years, he would be arrested several times, on charges ranging from DUI to failure to pay child support.

Miss Houston's moving 1991 rendition of "The Star-Spangled Banner" at the Super Bowl, amid the first Gulf War, set a new standard and reaffirmed her as America's sweetheart.

In 1992, she became a star in the acting world with "The Bodyguard." Despite mixed reviews, the story of a singer (Miss Houston) guarded by a former Secret Service agent (Kevin Costner) was an international success.

It also gave her perhaps her most memorable hit: a searing, stunning rendition of Dolly Parton's "I Will Always Love You," which sat atop the charts for weeks. It was Grammy's record of the year and best female pop vocal, and the "Bodyguard" soundtrack was named album of the year.

She returned to the big screen in 1995-96 with "Waiting to Exhale" and "The Preacher's Wife." Both spawned soundtrack albums, and another hit studio album, "My Love Is Your Love," in 1998, brought her a Grammy for best female R&B vocal for the cut "It's Not Right But It's Okay."

But during these career and personal highs, Miss Houston was using drugs. In an interview with Oprah Winfrey in 2010, she said that by the time "The Preacher's Wife" was released, "(doing drugs) was an everyday thing. ... I would do my work, but after I did my work, for a whole year or two, it was every day."

In the interview, she blamed her rocky marriage on Brown. The two divorced in 2007.

She went to rehab twice before she declared herself drug-free to Winfrey in 2010. But in the interim, there were missed concert dates, a stop at an airport due to drugs, and public meltdowns.

Her crude behavior and jittery appearance on Brown's reality show, "Being Bobby Brown," was an example of her sad decline.

Miss Houston staged what seemed to be a successful comeback with the 2009 album "I Look To You." The album debuted on the top of the charts, and went platinum.

Things soon fell apart. A concert to promote the album on "Good Morning America" went awry as her voice sounded ragged and off-key.

A world tour launched overseas confirmed suspicions that she had lost her voice, as she failed to hit notes and left many fans unimpressed; some walked out.

Canceled concert dates raised speculation that she may have been abusing drugs, but she denied those claims and said she was in great shape, blaming illness for cancellations.