More than 400 cases of an Omicron sub-variant have been identified across England.
According to authorities, 426 cases of Omicron BA.2 infections have been confirmed.
The earliest case is dated December 6, 2021, by Whole Genome Sequencing in England.
London and the South East have been identified as the areas with the largest number of confirmed cases - the capital has 146 cases and the South East has 97.
More analysis is being carried out on the sub-variant, about which little is known at this stage, The Mirror reports.
It is not known where BA.2 first originated. So far 40 countries have uploaded a total of 8,040 BA.2 sequences since mid-November.
The first sequences were submitted from the Philippines and the highest number of samples have been uploaded from Denmark, where 6,411 cases have been found.
Other countries that have uploaded more than 100 samples are India (530), Sweden (181), and Singapore (127).
The UK Health Security Agency (UKHSA) says the emergence of new mutations is not unexpected.
Dr Meera Chand, COVID-19 Incident Director at UKHSA, said: “It is the nature of viruses to evolve and mutate, so it’s to be expected that we will continue to see new variants emerge as the pandemic goes on.
"Our continued genomic surveillance allows us to detect them and assess whether they are significant.
"So far there is insufficient evidence to determine whether BA.2 causes more severe illness than Omicron BA.1, but data is limited and UKHSA continues to investigate.
“Case rates remain high throughout the UK and we must remain vigilant and take up vaccinations. We should all continue to test regularly with LFDs and take a PCR test if symptoms develop”.
In a statement, the UKHSA said: "As is routine for any new variants under investigation, UKHSA is carrying out laboratory and epidemiological investigations to better understand the characteristics of this variant.
"We will continue to monitor this situation closely and recommend appropriate public health measures if needed.
"More detail will be available in UKHSA’s regular Variant Technical Briefings."
In the past seven days nearly 650,000 new Covid cases have been confirmed by the Department of Health, but this. is a drop of 27 per cent compared to the previous week.
A further 95,787 UK cases were confirmed yesterday afternoon, Friday, January 21.
Tragically the Department of Health said 288 people have died within 28 days of testing positive for coronavirus, bringing the government's official death toll to 153,490.
England's Health Secretary Sajid Javid said: “We are learning to live with this virus - and thanks to our world-leading surveillance system we can rapidly detect and carefully monitor any genetic changes to COVID-19.
“Our exceptional vaccine rollout means the number of people severely affected by COVID-19 is low, and the UK’s innovation and research have discovered life-saving treatments for those most at-risk from COVID-19.
“As we cautiously return to Plan A, I encourage you to give yourself and your loved ones the best protection possible and Get Boosted Now.”
