Three poultry workers who showed signs of illness after a fellow worker tested positive for bird flu do not have the disease, health officials say.
Culling of chickens in North Tuddenham has begun
The trio displayed symptoms of conjunctivitis after a bird flu outbreak at a farm in Norfolk.
It comes after another worker at the farm contracted the less serious H7 strain of the infection in his eyes.
Bird flu - thought to be the H7 strain - has now been detected at three poultry farms near Norwich.
On Sunday, two farms were named as Norfolk Road Farm and Mowles Manor Farm, both in North Tuddenham.
They are approximately two miles away from Witford Lodge Farm, the scene of the original outbreak last week, where some 35,000 chickens were slaughtered.
Culling of chickens at Norfolk Road Farm has been taking place, after preliminary tests indicated they had the H7 strain of bird flu.
Both farms are run by local farmer Geoffrey Dann and his son Simon.
Geoffrey Dann's wife Gillian, speaking from their farmhouse in the village, declined to comment on the latest outbreak.
The government said initial tests showed the farms were affected by a less serious strain than the deadly H5N1 which killed a swan in Fife.
Two free range flocks would be slaughtered, officials said.
The Department for Environment, Food and Rural Affairs (Defra) said that preliminary results indicated the farms were affected by the H7N3 strain of avian flu.
Restrictions are now in operation for the 1km area around the affected sites in Norfolk, trading standards officials have said.
David Collinson, Norfolk County Council's Head of Trading Standards said the orders meant vehicles passing through the restricted zone carrying poultry or captive birds should not stop within it.
"The orders advise all bird keepers within a declared zone to maintain high standards of biosecurity and any movements of poultry and other captive birds within the zone must be licensed by a veterinary inspector," he said.
He stressed that roads and footpaths in the zone remained open and there were no restrictions on eggs or birds bought from any shop in or outside the zones.
Officials have said risk to the public remained "extremely low".
"H7 avian flu remains largely a disease of birds," said Dr Jonathan Van Tam, a flu expert at the Health Protection Agency.
"The virus does not transmit easily to humans, as evidenced by the small number of confirmed infections worldwide to date."
The three workers who were suspected of having conjunctivitis work at a slaughterhouse owned by Banham Poultry, which runs Witford Lodge Farm.
They underwent tests and specimens were sent to the regional HPA laboratory but the results came back negative and their symptoms are not linked to bird flu, an HPA spokeswoman said.
The strain found at Witford Lodge Farm, which is in North Tuddenham about 13 miles (20km) west of Norwich, was also the H7 type.
It is virulent among chickens but less of a threat to humans than the H5N1 variant.
Last month a swan in Cellardyke, Fife, tested positive for H5N1 - the only confirmed case in the UK so far.
The H5N1 virus has killed more than 100 people in Asia.
But experts say it does not pose a large-scale threat to humans as bird flu cannot pass easily from one person to another.
However, some experts fear the H5N1 virus could mutate and trigger a flu pandemic, potentially putting millions of human lives at risk.