Amy Winehouse may have been dead for up to six hours before a security guard assigned to watch her found her body in bed around 4 p.m. on Saturday.

The five-time Grammy winner told her security team that she was going to sleep, speaking to them last at 10 a.m. Rigor mortis has set in by the time she was found, which suggests she had been dead for several hours.

Britain's "The Sun" quoted sources saying that Winehouse, 27, had seen a doctor Friday night as part of a routine of checkups -- a result of her addiction problems -- but the doctor saw nothing wrong.

Apparently, Winehouse had been strong enough that same night to play a drum kit in her bedroom loud enough for neighbors to complain.

And while the cause of death is still unknown - a toxicology report could take weeks - many have speculated, in light of her addiction battle, that her premature death is the result of an overdose. British news outlets reported that Winehouse was in a drug and alcohol binge fog in the week leading up to her death. Some even report that she purchased a pile of powerful narcotics at a London pub the night before.

But according to a police source, there was no paraphernalia or sign of drugs in Winehouse's Camden home, People.com reported.

Her father, Mitch, made an appearance at his daughter's Camden house Monday to thank the fans who had built a shrine to his daughter in flowers and memorabilia. He said the family was "devastated and speechless."

"I can't tell you what this means to us. It really is making this a lot easier for us," he said of the tribute. "Amy was about one thing, and that was love. Her whole life was devoted to her family and her friends, and to you guys as well," he told fans.

Winehouse's friend and PR man Chris Goodman tells the Sun that she had suffered setbacks in recent weeks, but had relapsed over the past month.

"Her death has come as a great shock. She was a fantastic talent and a sweet girl," Goodman said.

Police have not yet released an official cause of Amy Winehouse's death, and an autopsy to determine the official cause will not be performed before Monday morning, authorities say.