Scotland Yard said Tuesday that "material relating to a forthcoming inquest" into Winehouse's death was delivered to an incorrect address.
The force declined to elaborate on the nature of the material but said it has been recovered. Inquiries are ongoing into how it ended up in the wrong place.
Police said the mix-up will not delay the reopening Wednesday of the inquest into Winehouse's death.
Winehouse, who had fought drug and alcohol problems for years, was found dead in bed at her London home on July 23 at age 27.
An initial autopsy proved inconclusive. The inquest was previously adjourned with no cause of death.