But the question of how the virus arrived in Suffolk remained unanswered as deputy chief vet Fred Landeg said there was "no evidence of illegal or unsafe movements of poultry" by Bernard Matthews from Hungary to the UK.

While scientists struggled to piece together the cause of the outbreak, confidence in the region's £2bn poultry industry continued to be eroded.

Government scientists revealed the H5N1 virus which killed turkeys on the Bernard Matthews farm at Holton, near Halesworth, was 99.96pc similar to the strain which infected geese in southern Hungary.

It set the UK at loggerheads with the European Commission and the Hungarian authorities, who had claimed on Monday that Hungary was not to blame for the Suffolk outbreak.

There was a growing suspicion in government circles that the virus may have been brought to the UK from areas until now thought to be clear of avian flu.

While this would clear Bernard Matthews of any wrongdoing, it would make the task of tracing the movement of the virus still harder.

Analysis of the virus came as the first consignment of turkeys arrived at the Holton plant after the government gave the go-ahead to restart operations.

It started processing turkeys again after being given the okay by public health and food hygiene officials following complete disinfection of the site.

Bernard Matthews said the reopening of the plant had been agreed by Defra, the State Veterinary Service and the Meat Hygiene Service.

But while operations returned to normal at Holton, sales of Bernard Matthews products continued to fall at supermarkets across the UK in the face of more negative headlines.

The Morrisons supermarket chain confirmed that sales of poultry, including Bernard Matthews products, have fallen 10pc in the past few days, while sales have fallen too at the biggest supermarket chain, Tesco.

Source: EDP24