Four members of staff at a B&Q distribution centre in Swindon have tested positive for Covid-19.
A spokesperson said those affected were self-isolating and colleagues had been contacted through the track and trace procedure.
The town was added to Public Health England's coronavirus watchlist last week, following a spike in cases.
Swindon Borough Council has launched a campaign to encourage people to minimise the spread of the virus.
A B&Q spokesperson said: "Of the colleagues contacted through the local track and trace procedure, all self-isolated immediately and were tested to confirm it was safe for them to return to work.
"Two colleagues are awaiting their test results and are continuing to self-isolate."
A new mobile testing unit has been set up next to the County Ground in the town centre.
The new cases in the area include a member of staff at McDonald's on the Greenbridge retail park, and an outbreak at an Iceland food distribution centre.
Two positive cases were also confirmed at Swindon's Poundland store on Wednesday.
Positive tests at the Bakkavor bakery in Devizes, about 20 miles (30km) away, have risen to 15 - up from seven at the end of last week.
The company said that staff who test positive will receive a "top-up" payment to full basic pay if they do not receive company sick pay.
Earlier this week thousands of households in the SN1 and SN2 areas were sent a letter reminding them of the advice they need to follow, after the latest data showed a high proportion of new confirmed cases in those postcodes.
Steve Maddern, the council's director of public health, said: "The recent rise in cases and the government highlighting us as an 'area of concern' is a wake-up call to us all.
"We cannot even begin to think we are coming to the end of this public health crisis."
People are being asked to stay at home, even if they have mild symptoms, and anyone who does show signs should book a test and not leave home for at least 10 days.
A council spokesman said: "Health chiefs in the borough are reminding residents to protect themselves and others by continuing to wash their hands, cover their faces if in enclosed spaces, and to stay at least one metre apart from people not in their own household."
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