About 200 farm workers are isolating after 73 people tested positive for Covid-19.
The cases have been found among the workforce of vegetable producers AS Green and Co, based in Mathon in Herefordshire.
Workers are being asked to remain on the farm during a period of isolation, while Herefordshire Council arranges food and essential supplies.
The firm is also being supported by Public Health England (PHE).
It said its staff were its “priority”.
The workers, who carry out picking and packing work during the harvesting season, live in mobile homes on the farm, near Malvern, in Worcestershire.
As a precaution, the council said, they were being treated as “one extended bubble” and were staying within household groups on the farm.
Katie Spence, PHE Midlands health protection director, said the company had implemented a range of infection control measures, including on-site testing, social distancing in communal areas and the indoor packaging area, encouraging regular hand washing and promoting the use of face coverings in closed areas.
“Despite these measures, a small number of workers became symptomatic earlier this week and they and a few close contacts among the workforce were tested initially and found to be positive,” she said.
Karen Wright, director of public health for Herefordshire, said: “Prompt testing on the farm has allowed us to understand transmission and control the spread of infection.
“We continue to support the farm management, their workers, who form an important part of our local economy, and the local community through this challenging time.”
A spokesperson for AS Green added: “Our staff are our priority, they are hard-working key workers helping us provide food for the country during these unusual times.”
From 29 June to 5 July, Herefordshire had a rate of two new cases per 100,000 people, figures from Public Health England show. This compares with Leicester which had 116 cases per 100,000.
Overall, the Herefordshire council area had seen 749 cases as of 7 July.