The judge in the Stephen Lawrence murder trial urged police today not to "close the file" on catching the rest of his killers.
Mr Justice Treacy made his appeal as Metropolitan Police Commissioner Bernard Hogan-Howe said that the remaining culprits "should not rest easily in their beds".
It is understood that police plan to meet next week to assess where the case stands.
Gary Dobson, 36, and David Norris, 35, received life sentences at the Old Bailey today for the racist murder of Mr Lawrence nearly 19 years ago.
The court has heard that a gang of five or six white youths set upon the A-level student in Eltham, south east London, in 1993.
Dobson, who is already serving a five-year sentence for drug-dealing, was sentenced to at least 15 years and two months.
Norris was given a minimum of 14 years and three months for the murder, which the judge said was a "terrible and evil crime".
Mr Lawrence's father Neville told reporters outside court that he hoped the pair would "give up the rest of the people" involved.
His mother Doreen said the sentences were "quite low", but she appreciated the judge's hands were tied and she would now "start moving on".
In court, Mr Justice Treacy called forward Detective Chief Inspector Clive Driscoll, who has been the senior officer in the case for a number of years.
He told him that the public inquiry into the circumstances surrounding Mr Lawrence's death had "shamed and humbled" the Met, but praised the hard work done in recent years.
The judge went on: "At least a measure of justice has been achieved at last. However, the convictions of Gary Dobson and David Norris will not, I hope, close the file on this murder. On the evidence before the court, there are still three or four other killers of Stephen Lawrence at large.
"Just as advances in science have brought two people to justice, I hope the Metropolitan Police will be alert to future lines of inquiry, not only based on developments in science but perhaps also information from those who have been silent so far, wherever they may be."
Earlier, he had sentenced Dobson and Norris in a packed but silent courtroom.
He called the killing "a terrible and evil crime", and quoted the Lord Chief Justice who called it a "murder which scarred the conscience of the nation".
Mr Justice Treacy told the pair: "A totally innocent 18-year-old youth on the threshold of a promising life was brutally cut down in the street in front of eyewitnesses by a racist, thuggish gang.
"You were both members of that gang. I have no doubt at all that you fully subscribed to its views and attitudes."
He said the murder was committed "for no other reason than racial hatred".
The evidence in the trial could not prove who wielded the knife, but he said that whoever used it had done so with Dobson and Norris's "knowledge and approval".
Neither of them had shown "the slightest regret or remorse" since the murder and they had both lied to the court.
When it was over, Dobson left speedily, stepping over Norris who had bent down to pick up his papers.
Norris then kissed his hand and offered it up to the public gallery in a thumbs-up sign before he too was led from the court.
As the judge rose to leave, a few people began clapping in the public gallery.
Dobson's father, Stephen, called down to the court: "Shame on all of you."
It is understood that a decision will be made on whether to keep the men at Belmarsh prison, in south east London, where Norris has previously been beaten up.