Dozens of food processing plants are dealing with coronavirus outbreaks, with one chicken factory forced to partially close after seeing a rise in the number of positive cases.

The Food Standards Agency (FSA) said as of Tuesday there are around 40 food processing plants in England, both meat and non-meat, with active outbreaks – but assured that the number “remains very low”.

One of those factories includes Banham Poultry in Attleborough, Norfolk, where 75 workers tested positive for coronavirus.

Norfolk County Council said in a statement on Thursday that tests were carried out on 347 members of staff after seven caught the virus.

As a result of the infection rate, which is at about 22%, Banham Poultry closed part of its site following advice from Public Health England and Norfolk Public Health.

The council said 350 workers will be asked to isolate with their households, while those who tested positive will be asked to isolate for 10 days.

Those who have tested negative will be asked to isolate for 14 days and the area of the factory affected will be deep cleaned, it added.

Norfolk’s director of public health, Dr Louise Smith, said the workers who tested positive lived around the county mainly in the Breckland, Norwich, and Great Yarmouth districts.

She said there is no evidence of increased risk to the general public, and that partially closing the factory was “the most effective way to protect the wider public from further transmission”.

FSA chief operating officer Colin Sullivan said: “Whilst the picture keeps evolving, the level of Covid-19 outbreaks in food processing plants that have been reported in this country remains very low and we continue to work with colleagues leading on these public health and health and safety issues.

“Across England, Wales and Northern Ireland there are more than 20,000 food processing plants and only a very small proportion have been impacted.”