Six years after Britain's only Nazi war crimes trial, police are once again investigating claims Nazis involved in World War II are living in the UK.
Anthony Sawoniuk was given two life sentences in 1999
Scotland Yard said its crimes against humanity unit launched an inquiry earlier this year.
It said the material to be investigated included a list of names passed to police by an MP.
Anthony Sawoniuk, a British Rail ticket collector, was found guilty in 1999 of murdering 18 Jews in Belarus.
Andrew Dismore, a Labour MP for Hendon in north London, told the Press Association news agency he had given "various names" to the police.
He said the names included "unaccounted for SS [elite Nazi troops] who may be in the country, or people living in the UK who are worth investigating".
Mr Dismore said pursuing war criminals of the past was a good way to deter war crimes in the future.
"These people should never be allowed to sleep easy in their beds, they should know that one day there may be a knock on the door," he said.
Scotland Yard's crimes against humanity unit, formerly called the war crimes unit, was scaled down after lines of inquiry under the War Crimes Act 1991 had been exhausted.
A Met spokesman said: "When subsequent allegations are received appropriate inquiries are carried out."
He said the unit was talking to government departments to decide the best way of dealing with the investigation.
Anthony Sawoniuk, originally from Domachevo, Belarus, died in Norwich prison last November at the age of 84.