More surge testing will be rolled out in Ealing after additional cases of the coronavirus variant first identified in South Africa were detected.
It is an extension of testing which was started in the west London borough earlier this month following the discovery of previous cases.
Cases have been identified in Acton, Greenford, Southall and West Ealing and are not believed to be linked to international travel.
People living in Ealing are strongly encouraged to take a COVID-19 test when offered.
Anyone with symptoms should book a free test online or by phone to get tested at a testing site or have a testing kit sent home.
On Wednesday the government announced that surge testing would begin in the HP10 postcode in Buckinghamshire and SW8 and SW9 postcodes in Lambeth in London.