Whitney Houston, who ruled as pop music's queen until her majestic voice and regal image were ravaged by drug use, has died at the age of 48.

Police responded to an emergency call at the Beverly Hilton hotel in Los Angeles at about 3:45 p.m. PT, said Lt. Mark Rosen with the Beverly Hills police. Paramedics who were already at the hotel because of a Grammy party rushed to Houston's fourth-floor suite and attempted to revive her but they were unsuccessful, Rosen told KABC-TV.

Houston was pronounced dead just before 4 p.m., Rosen said. Her body remained at the hotel while detectives were investigating.

"There were no obvious signs of any criminal intent," Rosen said.

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

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

Houston's longtime mentor Clive Davis held his annual pre-Grammy concert and dinner Saturday at the Beverly Hills Hilton. It was a bizarre scene as stars walked the red carpet amid a heavy police presence while news vans snaked around the block and paparazzi staked out every hotel exit.

Stars including Dr. Dre, Adam Lambert, Serena Williams and Kim Kardashian were in attendance.

In another development, Sunday's Grammy Awards show will feature a "musical tribute" to Houston by Jennifer Hudson. A spokesman for the show said Houston's death is too fresh to do more, but they had to note the Grammy-winner's amazing accomplishments.

Reaction online Condolences poured in via social media websites, particularly on Twitter, following news of Whitney Houston's death: "Heartbroken and in tears over the shocking death of my friend, the incomparable Ms. Whitney Houston." — Mariah Carey .

. "We have lost another legend. Love and prayers to Whitney's family. She will be missed." — Christina Aguilera .

. "I am absolutely heartbroken at the news of Whitney's passing." — Quincy Jones .

. "No words! Just tears." — Rihanna .

. "The voice of an Angel, the Heart of a Lamb, the spirit of a Lioness, the presence of a Goddess, love you R.I.P Whitney Houston." — Wyclef Jean .

. "I've know Whitney since she was a little girl and I loved her. She was like family to me. I will miss her." — Smokey Robinson .

. "It's so stunning and unbelievable. I couldn't believe what I was reading coming across the TV screen." — Aretha Franklin.

Expected appearance

Houston was supposed to appear at the gala, and Davis had told The Associated Press that she would perhaps perform: "It's her favourite night of the year … (so) who knows by the end of the evening," he said.

Houston had been at rehearsals for the show Thursday, coaching singers Brandy and Monica, according to a person who was at the event but was not authorized to speak publicly about it. The person said Houston looked disheveled, was sweating profusely and liquor and cigarettes could be smelled on her breath.

Two days ago, she performed at a pre-Grammy party with singer Kelly Price.

At her peak, Houston was the golden girl of the music industry. From the middle 1980s to the late 1990s, she was one of the world's bestselling artists. 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.

She influenced a generation of younger singers, from Christina Aguilera to Mariah Carey, who when she first came out sounded so much like Houston that many thought it was Houston.

Addiction woes

But by the end of her career, Houston became a stunning cautionary tale of the toll of drug use. Her album sales plummeted and the hits stopped coming; her once serene image was shattered by a wild demeanour and bizarre public appearances. She confessed to abusing cocaine, marijuana and pills, and her once pristine 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," Houston told ABC's Diane Sawyer in an infamous 2002 interview with then-husband Bobby Brown by her side.

It was a tragic fall for a superstar who was one of the top-selling artists in pop music history, with more than 55 million records sold in the United States alone.

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.

Houston first started singing in the church as a child. In her teens, she sang backup for Chaka Khan, Jermaine Jackson and others, in addition to modeling. It was around that time when music mogul Clive Davis first heard Houston perform.

"The time that I first saw her singing in her mother's act in a club … it was such a stunning impact," Davis told Good Morning America. "To hear this young girl breathe such fire into this song. I mean, it really sent the proverbial tingles up my spine."

Before long, the rest of the country would feel it, too. Houston 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 like Where Do Broken Hearts Go and I Wanna Dance With Somebody.

Early critical praise

The New York Times wrote that Houston "possesses one of her generation's most powerful gospel-trained voices, but she eschews many of the churchier mannerisms of her forerunners. She uses ornamental gospel phrasing only sparingly, and instead of projecting an earthy, tearful vulnerability, communicates cool self-assurance and strength, building pop ballads to majestic, sustained peaks of intensity."

Houston's decision not to follow the more soulful inflections of singers like Franklin drew criticism by some who saw her as playing down her black roots to go pop and reach white audiences. The criticism would become a constant refrain through much of her career. She was even booed during the Soul Train Awards in 1989.

"Sometimes it gets down to that, you know?" she told Katie Couric in 1996. "You're not black enough for them. I don't know. You're not R&B enough. You're very pop. The white audience has taken you away from them."

In this Oct. 13, 1997 file photo, Whitney Houston looks over her shoulder as her then husband Bobby Brown looks to her at the premiere of the movie Cinderella in Los Angeles. (Rene Macura, File/Associated Press)

Some saw her 1992 marriage to former New Edition member and soul crooner Bobby Brown as an attempt to refute those critics. It seemed to be an odd union; she was seen as pop's pure princess while he had a bad-boy image, and already had children of his own. (The couple had a 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.

But Houston said their true personalities were not as far apart as people may have believed.

"When you love, you love. I mean, do you stop loving somebody because you have different images? You know, Bobby and I basically come from the same place," she told Rolling Stone in 1993.

"You see somebody, and you deal with their image, that's their image. It's part of them, it's not the whole picture. I am not always in a sequined gown. I am nobody's angel."