Tens of thousands more birds are to be culled after Government vets were unable to rule out the spread of avian flu.
A total of 63,000 birds will be destroyed in the coming days.
Officials at the Department for Environment, Food and Rural Affairs (DEFRA) made the announcement following inspections of premises close to the centre of the initial outbreak at a hatchery in Pilling.
It is a week since the disease was discovered in a pheasant flock at HyFly game hatcheries, based in Pilling Lane, Preesall.
There 10,000 birds either died or had to be destroyed.
A further outbreak was reported on Friday at premises with a ‘business link’ to the hatchery, resulting in the culling of a further 1,000 birds.
The disease has not been confirmed at the third site which Defra officials said also had ‘business links’ to the initial outbreak.
But because the presence of the disease could not be ruled out in the flock, it was deemed necessary to carry out a cull.
A DEFRA spokesman said: “Following continued investigations it has not been possible to rule out the presence of disease in farmed birds at a further linked premises in the area.
“In order to contain the possible spread of disease, the Chief Veterinary Officer Nigel Gibbens has confirmed that proactive culling of 63,000 birds, including pheasants, partridges and ducks, will take place.
“The premises will then be cleansed and disinfected, further reducing the risk that disease can be spread to other birds.
“Our investigations will continue and the restrictions already placed on the sites will remain in force until cleansing and disinfection is finished and the investigation is complete.
“Public Health England advises that the risk to public health from the virus is very low and the Food Standards Agency is clear that bird flu does not pose a food safety risk for UK consumers.”
A 3km protection zone has been placed around the farms with restrictions on the movement of poultry and some other livestock.
A wider 10km surveillance zone, stretching as far as Anchorsholme, has also been established.