The search for the unidentified person who has tested positive for the Brazilian variant of Covid in the UK has been narrowed to 379 households in the south east of England.
Speaking in the Commons on Tuesday, Matt Hancock said the government was contacting “each one”.
Six cases of the variant, known as P1, have been found in England and Scotland.
But on Monday health officials announced they were still hunting for the identity of one of the six.
Hancock said: “We know that five of these six people quarantined at home as they were legally required to do.”
“Unfortunately one of these six cases completed a test but didn’t successfully complete the contact details. Incidents like this are rare and only occur in around 0.1% of tests.”
The health secretary told MPs: “We’ve identified the batch of home test kits in question, our search has narrowed from the whole country down to 379 households in the south-east of England and we’re contacting each one.
“We’re grateful that a number of potential cases have come forward following the call that we put out over the weekend.”
Hancock said the current vaccines being rolled out had not yet been studied against the P1 variant.
“We’re working to understand what impact it might have, but we do know that this variant has caused significant challenges in Brazil,” he said.
“We’re doing all we can to stop the spread of this new variant in the UK, to analyse its effects and to develop an updated vaccine that works on all these variants of concern and protect the progress that we’ve made as a nation.”
He added: “We have no information to suggest the variant has spread further.”
This article originally appeared on HuffPost UK and has been updated.