A computer disc containing sensitive information in connection with the shooting of Mark Duggan has gone missing.
The killing of Mr Duggan in Ferry Lane, Tottenham, in August 2011 sparked widespread rioting in London and other major cities.
Scotland Yard confirmed it was examining the case.
A police statement said: "We have carried out a full risk assessment on the material that we have been informed was on the disc, and have taken the necessary steps.
"Due to the nature of the material we are not prepared to discuss what those steps entail. The Metropolitan Police Service has offered its full support in attempting to locate the disc."
UK data watchdog The Information Commissioners Office is also looking into the case.
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