Whitney Houston mourned as Grammys begin
Fans and musicians have reacted with shock to the death of American singer and actress Whitney Houston.
Aretha Franklin, the star's godmother, said the news was "stunning and unbelievable" while Mariah Carey said she was "heartbroken and in tears".
Houston, 48, died in her Los Angeles hotel room. She had been due to attend Sunday's Grammy Awards ceremony, which will present a special tribute.
Singers Jennifer Hudson and Chaka Khan will perform in her honour.
As a 15-year-old, Houston sang backing vocals on Chaka Khan's hit I'm Every Woman.
Houston went on to become known for powerful ballads such as I Will Always Love You and One Moment In Time.
But her later career was overshadowed by substance abuse and her turbulent marriage to singer Bobby Brown.
Following news of her death, a visibly distraught Brown took to the stage in Southaven, Mississippi, with his band New Edition on Saturday evening.
Opening the show, he pointed to the sky and declared, "I love you".
Addressing fans, he added: "First of all, I want to tell you that I love you all. Second, I would like to say, I love you Whitney. The hardest thing for me to do is to come on this stage."
The couple's volatile marriage, which was marked by drug addiction and allegations of domestic abuse, ended in 2007.
After that, Houston's career appeared to be set for a revival. Her 2009 comeback album, I Look To You, reached number one in the US, and she had recently finished filming a new movie, Sparkle.
The singer's publicist Kristen Foster announced on Saturday that the singer had died. Police sources later confirmed that she had been found unresponsive in her hotel room at the Beverly Hilton Hotel.
Celebrity news website TMZ.com said the singer had been found slumped in the bathtub by members of her entourage, her face underwater.
Police investigators inspected the scene before Ms Houston's body was moved from the hotel to the coroner's office for an autopsy.
An autopsy is likely to be held within the next two days. However, if drugs or alcohol are involved, it will take between six and eight weeks for toxicology tests to be completed.
Meanwhile, Houston's 18-year-old daughter Bobbi was released from hospital after being treated following her mother's death.
The singer's death came on the eve of the Grammy Awards in Los Angeles. She had been due to attend a pre-awards party in the hotel she was staying in, organised by her long-time mentor and record industry executive Clive Davis on Saturday evening.
He went ahead with the party, holding a minute's silence and telling the audience he was "personally devastated by the loss of someone who has meant so much to me for so many years".
Jazz legend Herbie Hancock, who was attending the event, said: "It's difficult not to be sad about it because it's a great loss. Her soul, her spirit, lives within all of us."
R&B star Rihanna, who was rehearsing her Grammy performance when the news broke, simply tweeted: "No words! Just tears".
She later posted lyrics from Houston's biggest hits on her Twitter account, including "I have nothing if I don't have you", a track from the soundtrack to the star's biggest film, Bodyguard.
Music mogul Simon Cowell said he expected Sunday's ceremony to become a tribute to the singer, describing her as a "trailblazer and "legend".
"There are so few people like her in the world. They are a rarefied breed, these are true superstars, legendary divas - and I say divas in the nicest possible way.
"She had one of the greatest voices I have ever heard in my life, ever."
Civil rights activist Rev Al Sharpton said that on the morning of the Grammys, "the world should pause and pray for the memory of a gifted songbird".
Houston's background was steeped in soul and gospel music.
Her mother was gospel singer Cissy Houston, she was cousin to singer Dionne Warwick as well as having Aretha Franklin as godmother.
"I just can't talk about it now," Ms Franklin said in a short statement. "It's so stunning and unbelievable. I couldn't believe what I was reading coming across the TV screen."
Having grown up in New Jersey, Houston began singing in church and then in the night clubs of New York, and was a model before being signed by Arista Records.
To this day, she holds the record for having the most consecutive chart-topping singles in the US - reaching number one seven times between 1985 and 1988.
The first of those, Saving All My Love For You, set the template of towering, melismatic vocal performances - with Houston stretching single syllables out over dozens of notes.
Artists from Mariah Carey to Christina Aguilera have tried to emulate her bravura performances, but none of them were as good as the original, music critic Paul Gambaccini told the BBC.
Houston also enjoyed success acting in blockbuster films such as The Bodyguard and Waiting to Exhale.
Sony Pictures announced on Sunday that it would release the star's final film, Sparkle, which is loosely based on the story of The Supremes, in August.
"Like all those who knew and loved her, we are shocked and saddened," said spokesman Steve Elzer said on behalf of the studio. "The world has lost an incomparable talent."
The film also features Houston's final recordings - including a cover of the gospel standard His Eye Is On The Sparrow - which will be released on a soundtrack album over the summer.
In recent years drug use had taken its toll on the star and her voice - once acknowledged as one of the finest in pop music - was badly damaged.
She cancelled the first date of what was to be her final UK tour in 2010 citing respiratory problems. In her later performances, she was often said to be short of breath and unable to sustain the long, high notes that had been a hallmark of her career.
"The biggest devil is me. I'm either my best friend or my worst enemy,'' Houston told ABC's Diane Sawyer in a 2002 interview.
According to TMZ, Houston had been partying heavily on both Thursday and Friday nights.
She briefly took the microphone and performed a song while out in Hollywood on Thursday, and was seen drinking and chatting loudly with friends in the hotel bar on Friday, according to TMZ.
Despite her personal problems, she was still a widely-respected figure in the music industry.
Singer and X Factor judge Kelly Rowland paid tribute on Twitter, saying Houston had advised her in the early days of her career.
"I am beyond heartbroken. Whitney Houston was undoubtedly one of the greatest singers and performers of all time and such a huge influence of me [sic].
"She embraced me when I first started out with Destiny's Child, with love, with encouragement and with that powerhouse voice."
Country singer Dolly Parton - who wrote one one of Houston's most memorable hits, I Will Always Love You - said in a statement: "Mine is only one of the millions of hearts broken over the death of Whitney Houston."
"I will always be grateful and in awe of the wonderful performance she did on my song, and I can truly say from the bottom of my heart, 'Whitney, I will always love you. You will be missed'."
George Merrill and Shannon Rubicam, who wrote two of Houston's biggest hits How Will I Know and I Wanna Dance With Somebody (Who Loves Me), paid tribute to her "matchless" voice.
"I am grateful to her always for the gifts she brought to my life by recording - by so thoroughly rocking - our two songs," said Rubicam.
"So Whitney, from my heart, I honour you and wish you peace and joy, wherever you are."
Rap mogul P Diddy recalled the time he spent with the star, saying: "She always hit you with that beautiful smile, she always hit you with that incredible energy.
"She gave you that hug that, you know? That grandma hug that you know that just shook your body."