Turkeys culled at two farms over fears of exposure to bird flu have tested negative for the deadly H5N1 strain.
More than 28,000 birds have been culled
Birds at Stone House in West Harling and Bridge Farm in Pulham, both in Norfolk, were judged to have been in "dangerous contact" with the disease.
The farms are run by Redgrave Poultry, the owner of two farms in Norfolk and Suffolk, where H5N1 has been confirmed.
Tests on culled birds at a fifth premises - Grove Farm, in Botesdale, Suffolk - indicate it was disease-free.
In all, more than 28,000 turkeys, ducks and geese have been culled in a bid to prevent the deadly virus spreading.
Protection zones and an extended surveillance zone are in place around the two infected sites, with a wider restricted zone covering Suffolk and most of Norfolk.
The H5N1 outbreak was first confirmed at Redgrave Park Farm, in Redgrave, near Diss, on the Norfolk/Suffolk border, a week ago.
Birds at four other farms were considered to have been in dangerous contact with the outbreak because they had staff members in common with the affected farms.
On Monday, it was confirmed the culled birds at Hill Meadow Farm in Knettishall on the Norfolk/Suffolk border had been infected with H5N1.
Grove Farm, Botesdale, Suffolk, close to the first infected site, was upgraded to a slaughter on suspicion of having the disease last week after dozens of birds were found dead by officials.
But initial tests on 5,500 turkeys slaughtered found the premises was free of disease.
A new 3km protection zone around the Hill Meadow Farm case has been established and a wider surveillance zone covering both sites has also been imposed.
A national and a local disease control centre have been established in Bury St Edmunds, with text messages sent to all bird keepers nationwide - especially those in zones on the poultry register.
The cost of animal infections is thought to have cost the government and taxpayer more than £120m this year.