Police officers who worked on the original Stephen Lawrence murder inquiry in 1993 are being asked to contact the police watchdog.
Stephen Lawrence was attacked at a south-east London bus stop
The Independent Police Complaints Commission (IPCC) is examining claims made in a BBC documentary that the inquiry was marred by corruption.
The IPCC wants officers, or people who may have dealt with them, to contact them with any relevant information.
Stephen, 18, was stabbed to death in south-east London in 1993.
Five men - Neil Acourt, his brother Jamie, David Norris, Gary Dobson and Luke Knight - were arrested after the initial investigation but were never convicted.
A second police investigation revealed them to be a gang of racists who had an obsession with knives.
Nobody has ever been convicted of Stephen's murder but the Macpherson inquiry into the first police investigation concluded that the police were institutionally racist.
It prompted many changes in the British criminal justice system.
In July, a BBC documentary accused retired Det Sgt John Davidson of taking bribes from Clifford Norris, father of suspect David Norris. Mr Davidson has denied the claims, describing them as "devastating and false".
The claims were made by former corrupt detective turned whistleblower Neil Putnam and are now being investigated by the IPCC following formal complaints from Stephen's parents Doreen and Neville Lawrence.
IPCC deputy chairman John Wadham said they would be investigating whether any officers on the original inquiry might have received bribes.
They will also look at a separate claim by Mr Putnam that he reported his concerns at the time to the Met, but they were not investigated.
He said: "I would appeal for anybody who can throw light on these allegations to contact us.
"They may have served in the former South East Regional Crime Squad, worked in the Metropolitan Police or may be a member of the public who dealt with the first inquiry team into Stephen Lawrence's murder or those accused of bribery."
The IPCC has set up a special number, 020 7166 3973, and a special email address, email@example.com, for witnesses to contact them.