The Philippines has now reported 16 new cases of the more transmissible variant of the coronavirus.
The Health Ministry said on Friday that 12 of the 16 cases were recorded in Bontoc town, over 400km north of capital Manila.
Two Covid-19 infections by the variant were found in La Trinidad town and Calamba town, an hour's drive south of Manila.
The latter is an indication that the variant has possibly spread to the southern part of the country as well.
Both patients had not travelled abroad and had no contact with an already confirmed case.
Two others were overseas Filipino workers who had returned from Lebanon on Dec 29.
The new variant is probably already circulating in Baguio city, an urban hub in the country's north.
"We can safely assume that the variant is already in Baguio, considering inhabitants of Bontoc and La Trinidad come regularly to Baguio," said Mr Benjie Magalong, mayor of the city.
Meanwhile, a regional office of the Health Ministry in Cebu City, in central Philippines, said it was checking three likely cases of infection by the new variant.
The Philippines reported its first case of this variant - officially known as VUI-202012/01 or lineage B117 - on Jan 13. It was a 29-year-old real estate agent living in the capital who had gone to Dubai for business from Dec 27 to Jan 7.
Yesterday, health officials said the new variant - first detected in Britain in September - had apparently been in the Philippines as early as Dec 10, the day the case in Calamba town tested positive.
It was not known at the time that he was carrying the new variant.
The British variant is believed to be 70 per cent more transmissible than previously circulating coronavirus variants.
A tentative finding by researchers in London suggests that it may be deadlier than the original.
Health experts in the Philippines warned that the new variant could raise the country's total coronavirus caseload 15 times.
Dr John Wong, from health research institution EpiMetrics, said: "With our current reproduction rate of 1.1, 20,000 cases at the beginning of the month will become about 32,000 at the end of the month. But if the (new) variant takes over, the 20,000 cases can become almost 300,000 cases by the end of the month."