Nearly 300 employees have tested positive for coronavirus at a factory that makes sandwiches for M&S.
The Greencore factory in Northampton said some of its staff are now self-isolating after the COVID-19 diagnosis.
Greencore said 79 workers had tested positive through NHS tests before the company decided to bring in a private testing program.
A further 213 positive results came back - taking the total number of positive results to 292.
Greencore told Sky News that the company is still waiting for some results to come back. A spokesman was unable to confirm how many but said it was less than 100.
The company said in a statement: "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 PHE East Midlands, Northamptonshire County Council and Northampton Borough Council, who are fully supportive of the controls that we have on site."
The company added: "In each case we have immediately conducted contact tracing and instructed potentially affected colleagues to self-isolate.
"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.
"As ever, the health and wellbeing of our colleagues is our number one priority."