The source of the polio virus discovered in a London sewage works could be narrowed down to a house or street, a health minister has said.

Lord Kamall said relevant agencies were now using “world-beating” tools to work out how to “go along the pipe” to locate where the virus came from.

“In theory, it might be possible to find individual households or streets,” he added.

The UK Health Security Agency declared a national incident on Wednesday after traces of the virus were found during routine surveillance at the Beckton Sewage Treatment Works.