Heather Peck, Defra regional operations director for animal health, said more than 1,000 out of 25,000 chickens on Eastwood Farm had so far been slaughtered with culling due to continue tomorrow.

The measures are being taken after the H7 strain of Avian Influenza was confirmed at the farm on Tuesday.

"It is about doing the job humanely and without putting people at risk," she said.

"The birds are being caught by teams that are used to handling poultry without causing them injury or unnecessary stress.

"They are then being put into crates and gassed on site. They are then counted into bulk lorries which transport them to the rendering plant in Nuneaton.

"The lorries are escorted all the way in case there is an accident."

Ms Peck said Defra officials would be visiting farms in the 3km temporary control zone tomorrow and issuing advice.

"We will be giving a piece of paper to poultry keepers on our register and repeating the type of the information that has already been published in the press," she said.

"Once the culling has finished the next stage will be cleansing and disinfection. Then there will be a set period that the farm must remain empty."

Ms Peck said it was too early in the investigation to say exactly how at risk other farms were.

She also said it was difficult to compare the outbreak of the disease in Shenington with previous outbreaks.

"Some outbreaks in the past have involved turkeys, some have involved land foul and these bring a very different sort of challenge," she said.

"Every outbreak is different in the sense that every farm is different.

"They all vary and we have to adjust appropriately."