Police investigating the murder of Pc Keith Blakelock said they were "very confident" of catching his killers as they began searching a back garden.
Archaeologists are helping officers search the address
The Met said "first rate intelligence" had led police to searching an address in Tottenham, north London.
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.
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 in Tottenham.
A Met spokesman said: "At 0700 BST officers investigating the murder of Pc Blakelock and attempted murder of Pc Richard Coombes began a forensic excavation of the rear garden of 16 Willan Road, Tottenham."
He stressed that the current occupants were not suspects.
Commander Andy Baker said the Met was very confident that the search could help bring the killers to justice.
"We are searching for the truth. If we find out who the killers are we will put that before the Crown Prosecution Service and they will decide on that independently," he said.
He said the investigation was being undertaken "with an entirely open mind".
Pc Keith Blakelock was hacked to death
Father-of-three Pc Blakelock, who was posthumously awarded the Queen's Medal for Bravery, died after confronting rioters on the Broadwater Farm housing estate.
The riots began after 49-year-old Cynthia Jarrett collapsed and died of heart failure during a police raid on her home.
Detectives are also re-investigating the attempted murder of Pc Richard Coombes during the disturbances.
Both officers were attacked after they went into an estate in 1985 to protect firefighters.
Weapons were found at the time of the original murder but Pc Blakelock's helmet was never found.
'New lines of inquiry'
Mr Baker declined to discuss if the search was to try and recover the murder weapon or its importance to the case.
In recent weeks police have delivered more than 3,000 leaflets on the estate and surrounding areas to alert the community of what is happening.
The re-investigation into the crimes was announced last October, after a review process that began in 2000.
Mr Baker said new lines of inquiry were identified through the review, and these have formed the basis of the fresh investigation.
The search of the garden is expected to last three days.