The Met said advances in forensic techniques had led it to focus on an item recovered on the night of the murder.
It said those approached for DNA samples were not suspected of being involved in Stephen's murder.
Two men are currently in prison for the fatal stabbing 23 years ago.
The Met did not reveal any further details about the recovered item at the centre of its inquiries.
Eighteen-year-old Mr Lawrence was stabbed to death in an unprovoked attack at a bus stop in Eltham by a gang of white youths.
Gary Dobson and David Norris were found guilty of his murder and sentenced to minimum terms of 15 years and two months and 14 years and three months in January 2012.
The Met said it remains "firmly committed" to continuing to investigate the murder.
The National Crime Agency is currently investigating alleged police corruption during the original murder inquiry.
Two separate inquiries are being carried out - a judge-led public inquiry into undercover policing as a whole, which includes the Stephen Lawrence case amongst others, and one by the Independent Police Complaints Commission.
The IPCC is looking at a complaint by Mr Lawrence's father, Neville, concerning former Metropolitan Police commissioner John, now Lord, Stevens over claims he withheld evidence from the 1998 Macpherson Inquiry.
Police investigating the murder of Stephen Lawrence in 1993 have contacted an unspecified number of people to request DNA samples.