Northampton employees at the shut-down Greencore food factory and another site with a coronavirus outbreak were travelling to work in a car together, it has been confirmed.
There have also been 16 incidents of between two and four people living in houses in multiple occupation (HMOs) testing positive for Covid-19 and working at the Moulton Park Industrial Estate facility.
Northampton Borough Council leader Jonathan Nunn said they are all self-isolating and being traced but he also urged residents to avoid car-sharing and public transport but wearing a face covering if it is unavoidable.
"Car sharing is an issue, not only amongst the same workplace but there are some links with evidence to car-sharing between Greencore and one of the other outbreaks that's on a different industrial area but is of a much smaller scale," he said during a press conference yesterday (Friday, August 20).
"So some of this problem is not just all people from one factory jumping into a car, there are these links which are being traced.
"But the assurance is every single one of them is being traced to make sure that efforts, testing and everything else goes in to where these links may turn into further outbreaks or infections."
Northampton has been upgraded to an 'area of intervention' by the health secretary due to the coronavirus infection rate hitting 125.1 per 100,000 during the week ending August 13.
Greencore has voluntarily closed after being asked to by the government and workers have to self-isolate for two weeks, with fines threatened for non-compliance.
The Deer Park Road site will undergo a deep clean over the next few days before a staggered reopening but no date has been given yet.
Northamptonshire County Council director for public health Lucy Wightman insisted the factory, which supplies Marks and Spencer among others, should not have closed sooner.
The person in charge of the county's response to Covid-19 added that Greencore has 'demonstrated significantly higher levels of cooperation than required' - Cllr Nunn said the firm has behaved 'responsibly'.
"Although I appreciate the focus on Greencore because of the secretary of state's decisions, there is still a fight which we are fighting around Covid across the wider county," she said.
"Greencore clearly has a significantly influenced our figures but Northampton was already on the watchlist.
"We need to make sure we continue with all the good practice that has started and that we continue to push the numbers in the right direction so we can identify where these cases are and make sure we reduce the rate of transmission through self-isolation."
Ms Wightman said 85 per cent of Greencore employees live in Northampton and the next highest place is Wellingborough with a handful in other places both in and out of the county.
Cllr Nunn said they are working with Greencore to ensure workers are not tempted to find additional income after being told to self-isolate for two weeks while attendance figures will not be considered in bonus payments.
Staff may not have to if they have already self-isolated since the outbreak emerged, according to Ms Wightman, but the council leader said the authorities will make sure they do not go hungry.
"We're working with Greencore to ensure everybody has the money they need to pay the rent and cover the food bill," he said.
"Quite clearly, if someone is forced to be off work with far less than they need just to survive, then the possibility of taking another job or casual cash work on a building site or whatever it might be will be very strong, almost a necessity rather than just a temptation.
"So that is an area we're looking at very, very carefully to ensure that people do have the wherewithal to self-isolate should they need to and shouldn't be forced to move out of county to get off the radar and start earning money somewhere else."
Northampton was an 'area of concern' but following the outbreak of 292 Covid-19 cases at Greencore, the town has moved up to the highest level of government monitoring.
An 'area of intervention' is where there is divergence from the measures in place in the rest of England because of the significance of the virus' spread, with a detailed action plan in place, and local resources augmented with a national support, according to the government.
Specific advice for residents in Northampton, as well as those in Kettering, Corby and Wellingborough:
■ Limit contact with others outside of your household or bubble
■ Work from home if you can
■ Avoid using public transport or car sharing, wear face coverings if you cannot avoid these
■ Do not share items with others outside of your household or bubble
■ Even if you only have mild COVID-19 symptoms, get a test