Almost 300 staff have been forced into self-isolation after testing positive for the coronavirus at a Northamptonshire-based sandwich supplier for Marks & Spencer.

The supplier Greencore said a significant number of its staff had tested positive for the virus after it took the decision to test workers after a spike in infections in the town, according to The Guardian.

According to the local council, 79 staff at the supplier returned positive NHS tests and 213 of Greencore’s private tests came back positive.

The company said: “As a result of the rising number of Covid-19 cases in the Northampton area, we took the decision to start proactively testing all of the colleagues at our Northampton site. We can confirm that a number of colleagues have tested positive for the virus and are now self-isolating.

“We are liaising closely with Public Health England East Midlands, Northamptonshire county council and Northampton borough council, who are fully supportive of the controls that we have on-site.”

The news follows a similar outbreak at an Asda-owned meat processing site in West Yorkshire where 165 employees contracted the virus in June.

Globally, new coronavirus clusters have been linked to infections in food processing plants in France and in the US where 25,000 food factory workers may have contracted the disease. 

Greencore said it had carried out contact tracing with each confirmed case at its factory and the safety of its staff was its highest priority.

“All of Greencore’s sites have wide-ranging social distancing measures, stringent hygiene procedures and regular temperature checking in place, and we are doing everything that we can to keep our people safe,” it added.