Amy Winehouse may have been dead for up to six hours before her body was discovered lying in bed, police fear.
The star, 27, last spoke to her security team at 10am on Saturday. She was found at home in Camden, North London, at 4pm.
Medics said she'd been dead several hours.
Police sources reported no sign of drugs at the house.
Amy had seen her doctor on Friday night. Amy's doctor examined her the evening before her death - and gave her the all clear. The singer was having regular check-ups because her drink and drug battles had left her so frail.
A source said: "The doctor was happy with her condition. When he left on Friday night he had no concerns. Less than 24 hours later she was found dead.
"Amy's health has been very fragile and she has been having a series of check-ups."
Her cause of death is unlikely to be known until the police get the results of toxicology tests. That could take weeks.
But Amy's family last night said reports she had bought cocaine, ketamine and ecstasy hours before she died were "nonsense."
They added in a statement: "Our family has been left bereft by the loss of Amy, a wonderful daughter, sister, niece."
Police sources confirmed there were no signs of drugs in her three-story house.
Amy was found dead in bed at her home by her security guard Andrew Morris just before 4pm on Saturday.
Her friend and PR man Chris Goodman said: "Amy was on her own at home apart from a security guard who we had appointed to help look after her over the past couple of years.
"She was in her bedroom after saying she wanted to sleep and when he went to wake her he found she wasn't breathing.
"He called the emergency services straight away. He was very shocked.
"At this stage no one knows how she died. She died alone in bed."