Police investigating the Stephen Lawrence case have confirmed that they are re-examining the evidence surrounding his unsolved murder.
Stephen Lawrence was murdered in an unprovoked attack in 1993
Det Ch Insp Clive Driscoll said a forensic review began 18 months ago, but has "many months" to run.
The BBC understands police have made "potentially significant" findings but do not expect to make any arrests soon.
Police have not confirmed reports that they plan to re-arrest previous murder suspects following new forensic tests.
On Thursday the Daily Mail newspaper reported that five former suspects in the race-hate murder were set to be re-arrested following new tests on fibres found in Stephen Lawrence's clothing.
But Scotland Yard have played down reports of imminent arrests and are not confirming any details of their forensic tests.
Det Ch Insp Driscoll told the BBC: "We are doing a forensic review and we will be as thorough as we can. It's ongoing and has many months to run."
He said it was "standard practice" in the Metropolitan Police to review unsolved murders to see if any other evidence came to light.
He added that the review involved looking again at all the material amassed during the various inquiries and said that it should not be hurried or rushed.
Stephen, 18, was stabbed to death at a South London bus stop by a gang of five white youths in April 1993.
No-one was convicted of the killing but five men were arrested soon afterwards: Gary Dobson, 32, Neil Acourt, 32, Luke Knight, 31, Jamie Acourt, 31, and David Norris, 31.
Dobson, Knight, and Neil Acourt were acquitted of murder after a private prosecution - brought by the Lawrence family - collapsed at the Old Bailey in 1996.
Norris and Jamie Acourt never stood trial as the case against them collapsed before reaching court.
Two years ago, the government abolished the double jeopardy rule, which prevented defendants being tried twice for the same crime.