Surge testing is to be deployed in the London borough of Tower Hamlets after several cases of the South African and Brazilian variants were found.
Neither Tower Hamlets Council, nor NHS Test and Trace, has provided details of how many cases have been identified, but additional testing and genomic sequencing is due to take place in targeted areas within the E1 postcode from Sunday.
So far, variants of concern have been identified in Tower Hamlets in 10 sub-districts in the postcodes E1, E2, E3 and E14.
It comes as the government reported seven new coronavirus deaths and a further 1,907 infections on Saturday, taking the total number of deaths recorded within 28 days of a positive COVID-19 test to 127,524.
A statement from the Department of Health and Social Care (DHSC) said: "All the confirmed cases are self-isolating. There are no links between these cases and the cluster of cases recently identified in the south London area.
"Everybody aged 11 years and over who resides, works or is educated in these postcodes is strongly encouraged to take a COVID-19 PCR test when invited, whether they are showing symptoms or not.
"Enhanced contact tracing will be used for individuals testing positive with a variant of concern. In these instances, contact tracers will look back over an extended period in order to determine the route of transmission.
"By using PCR testing, positive results can be sent for genomic sequencing at specialist laboratories, helping us to identify variant of concern cases and their spread.
"People with symptoms should book a free test online or by phone so they can get tested at a testing site or have a testing kit sent to them at home."
The Brazilian variant identified, also known as P1, is the more serious of the two from Brazil, as it contains mutations that mean scientists fear it may be more able to bypass protection offered by the current vaccines.
There are concerns the South African variant, officially called B.1.351, also leaves vaccines less effective than it would have been with the original coronavirus variant.
Tower Hamlets council is asking people who want to find out if are being asked to get a test to go to its website and enter their postcode.
In the meantime, it is making tests more easily accessible by setting up an additional test site on Sunday 2 May at Gouldman House, E1 4HQ, from 8:30am to 3pm.
On Friday, it emerged that surge testing was being rolled out across four other postcode areas in east London, IG1 and IG6 postcodes, and small areas of IG5 and IG7, after cases of the South African variant were found.
A "significant" cluster of the South African variant was discovered in the Wandsworth and Lambeth areas of south London in mid April.
As of 28 April, 737 cases of the South African variant have been discovered in the UK so far, and 82 cases of the Brazilian P1 variant.