Police searching a garden in north London as part of the investigation into the murder of Pc Keith Blakelock say they have found "one item".
Ground-penetrating radar has been used to search the garden
Scotland Yard would not reveal what the item was, but said it would be sent for further forensic examination.
Pc Blakelock, 40, from Sunderland, was hacked to death by a mob during the Broadwater Farm riots in Tottenham.
Winston Silcott, Mark Braithwaite and Engin Raghip were convicted of the killing in 1987 but cleared on appeal.
Officers began digging up the garden on Tuesday as a result of receiving "first rate intelligence".
They have been using ground-penetrating radar which has identified a number of areas for immediate excavation.
But the Met said it was "too early to draw any conclusions about the item."
Archaeologists are helping a team of specialist search officers to search the garden of 16 Willan Road, a terraced house on the Broadwater Farm estate.