The 27-year-old singer had been troubled by drink and drugs problems throughout her career and news of her death was quickly followed by suggestions that it could be related to one or the other.
The troubled Back To Black artist cancelled all tour dates and engagements last month after a series of erratic public appearances.
But news that she had been found dead at her north London home just before 4pm yesterday came as a shock to many.
Her father, taxi driver-turned jazz singer Mitch Winehouse, was returning to the UK from New York where he had been due to give a concert on Monday.
A spokesman for the soul star said: ''Everyone involved with Amy is shocked and devastated. Our thoughts are with her family and friends.
"The family will issue a statement when ready."
London Ambulance Service said it was called to Winehouse's home in Camden Square at 3.54pm.
Two ambulance crews arrived at the scene within five minutes and a cycle responder also attended, according to a spokeswoman.
A section of the road where the singer lived was cordoned off, while fans and residents gathered at the police tapes, some laying flowers.
A neighbour who did not want to be named said she saw the singer's grief-stricken boyfriend on the ground outside the house.
Forensic officers were seen going in and out of the building and a black private ambulance pulled up outside the house at around 8.45pm.
Officials bearing a red body bag emerged minutes later.
As well as flocking to her home, fans also paid tribute at the Hawley Arms pub in Camden, once a favourite haunt of the pop star.
The pub said in a statement: ''We are shocked and deeply saddened by the news of Amy's death. Apart from her extraordinary musical talent, she was a special person with a good soul and this should not have happened.
''We feel privileged to have known her and we will sorely miss her.''
Speaking near Winehouse's home, a senior police officer said it would be ''inappropriate'' to discuss what killed her before a post-mortem examination had taken place.
Superintendent Raj Kohli said: ''Police were called by the London Ambulance Service to a house in Camden Square NW1 shortly before 16.05 today to reports of a woman found deceased.
''On arrival officers found the body of a 27-year-old female, who was pronounced dead at the scene. Next of kin have been informed and I can confirm that the deceased is Amy Winehouse.
''Inquiries continue as to the circumstances of the death. At this early stage it is being treated as unexplained. There have been no arrests in connection with this incident.
''I am aware of reports suggesting that the death was a result of a suspected drugs overdose, but I would like to re-emphasise that no post-mortem examination has yet taken place and it would be inappropriate to speculate on the cause of death.''
Tributes poured in from celebrities, among them her collaborator Mark Ronson.
The producer said in a statement: ''She was my musical soulmate and like a sister to me. This is one of the saddest days of my life.''
Sylvia Young, of Sylvia Young Theatre School, where a young Winehouse was given a half-scholarship, described the singer as ''a wild spirit'' who was also ''extremely bright''.
''We thought she would do very well in the musical field,'' she told the BBC. ''Certainly she was a wild spirit.
''She was her own person, she would follow what she wanted to do, there was no question about that.''
US singer Carole King, whose song Will You Love Me Tomorrow was covered by Winehouse, said she was ''very grateful'' the star had ''put her wonderful talent'' into recording the track.
King told BBC News: ''She did such a beautiful performance on it. I'm just grateful she gave that gift to Gerry (Goffin, the song's co-writer) and me and to the world. I just really hope that she's found peace now wherever she is.''
Winehouse joins the notorious ''27 Club'' of musicians who have died at that age after struggling to cope with fame.
They include Rolling Stone Brian Jones, who drowned in a swimming pool in 1969; guitarist Jimi Hendrix, who choked to death in 1970 after mixing wine with sleeping pills; and singer Janis Joplin, who suffered a suspected heroin overdose the same year.
Doors star Jim Morrison, who died of heart failure in 1971, and Nirvana frontman Kurt Cobain, who shot himself in 1994, are also members.
