American singer and actress Whitney Houston has died in Los Angeles at the age of 48.
Police said she died in her room at the Beverly Hilton Hotel, where she had been staying as a guest.
Houston was one of the most celebrated female singers of all time, with hits including I Will Always Love You and Saving All My Love For You.
But her later career was overshadowed by substance abuse and her turbulent marriage to singer Bobby Brown.
Ms Houston died on the eve of the Grammy Awards in Los Angeles. She had been due to attend a pre-awards party in the Beverly Hilton Hotel 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."
The hotel was already teeming with reporters and celebrities when police received an emergency call from hotel security at 15.43 local time (23:43 GMT), Beverly Hills police spokesman Mark Rosen told the BBC.
Police were despatched, but paramedics who were already at the hotel because of the party attempted to resuscitate her, without success. She was pronounced dead at 15:55.
Mr Rosen said Ms Houston's entourage - comprising family members, friends and co-workers - had taken over much of the fourth floor of the hotel.
"There were a number of people on scene who were able to positively identify Ms Houston for us," he said, adding that her next of kin have been informed of her death.
Police investigators inspected the scene before Ms Houston's body was moved from the hotel to the coroner's office for an autopsy.
While the cause of death is unclear, Mr Rosen said there were "no obvious signs of criminal intent".
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.
The US celebrity website TMZ.com reported that Ms 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.
Houston's background was steeped in soul and gospel music.
Her mother was gospel singer Cissy Houston, she was cousin to singer Dionne Warwick and goddaughter to Aretha Franklin.
"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.
At the height of her career in the 1980s and 90s she won many awards and enjoyed several number one singles and albums.
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.
Carey was one of the many singers to pay tribute to the star, saying she was "heartbroken and in tears over the shocking death of my friend".
"My heartfelt condolences to Whitney's family and to all her millions of fans throughout the world. She will never be forgotten as one of the greatest voices to ever grace the earth."
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."
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 did have it all, but the record is there of the decline into drug use and the damage done from drug use," said Gambaccini.
Her marriage to Brown, with whom she had a daughter, Bobbi Kristina, ended in divorce in 2007. The marriage had been a tempestuous one, with allegations of domestic abuse as well as drug addiction.
"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.
Ms Houston was strongly linked to the Grammys - having won six awards herself over the years. Organisers of Sunday's ceremony said she would be remembered in a special tribute by singer Jennifer Hudson.
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".
Country singer Dolly Parton - who wrote one one of her 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'."