A rural row is raging over the smells emitting from a farm with thousands of pigs.
Neighbours have complained that they are "under house arrest" due to the "stench, smell, pollution and toxic agents" from the business.
The UK Health Security Agency (UKHSA) has confirmed it is looking into complaints about ammonia pollution from Cherry Tree Farm at Stow Bedon, near Watton.
It says it is working with Breckland Council's environmental health department and the Environment Agency "to understand the situation in its entirety".
Wayland Farms was given planning permission to expand its operations to keep 6,990 swine on Cherry Tree Lane in 2019.
But a retrospective application to Breckland for further buildings, including a feed mill and electricity substation have been met with complaints from people living around the site.
Stow Bedon and Breckles Parish Council responded: "Almost on a daily basis our residents are sending complaints to the Environment Agency about breaches to the Permit they have issued with regard to odours and noise."
One resident said: "I have lost count of how many times I have complained to the Environment Agency regarding the stench, smell, pollution and toxic agents which continue to contaminate our home and environment, and still nothing is done.
"It is so distressing when the contamination occurs and we as a family are not able to venture outside, we are under house arrest, sentenced to be prisoners in our own home by not being able to open windows and doors on hot days or enjoy our gardens as the contamination stings our eyes and contaminates our food."
Another added: "The unit causes massive pollution incidents on a regular basis since it began operating two years ago."
In December, the Environment Agency told residents it had issued an enforcement notice "requiring the operator to give us a report into their investigations of the root cause of odour off-site".
South West Norfolk MP Liz Truss has passed residents' concerns on to the UKHSA, which said it would be meeting other agencies "to discuss the situation and plan next steps".
Wayland Farms, which is part of the Cranswick PLC group, has been contacted for comment.
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