London police say an autopsy on British singer Amy Winehouse has failed to determine how she died.

Forensic experts will now carry out toxicology tests, whose results could take several weeks.

A spokesman for the Winehouse family says she will be buried Tuesday in a private funeral to be attended only by family and close friends. Winehouse's parents stepped outside the singer's London home Monday to thank gathered mourners and fans for their support.

Winehouse was found dead Saturday inside her home. Police are calling her death unexplained, but say it is not suspicious.

The 27 year-old singer led a tumultuous life, struggling with drugs, alcohol, and abusive relationships even while critics and fans hailed her as a masterful blues and jazz artist. She gained worldwide success with her Grammy award-winning second album Back to Black.

But she also struggled to keep her career on track. She cancelled her European tour last month after an audience in Serbia booed her off the stage when she appeared to be disorientated and incoherent.