East Anglian poultry giant Bernard Matthews faced tough questions last night as the government said the strain of bird flu found at a farm in Suffolk may have been imported from Hungary.

East Anglian poultry giant Bernard Matthews is facing tough questions as the government said the strain of bird flu found at a farm in Suffolk may have been imported from Hungary.

Two days after the company “absolutely ruled out” any link between the disease at its plant at Holton, near Halesworth, and outbreaks of avian flu in Hungary, officials said the two viruses “may well be identical”.

Experts from Defra, the Food Standards Agency (FSA) and the Health Protection Agency (HPA) will now step up their investigation into the source of the Suffolk outbreak.

The company, which has a division in Sarvar, Hungary, agreed to suspend temporarily the movement of poultry products between its outlets in the two countries.

A team moved in to the Holton plant to slaughter 160,000 birds last week after 2,500 turkeys were killed by the virus.

Defra said: “The government is developing its investigation into what might have caused the outbreak of avian influenza in the Suffolk poultry farm, following preliminary scientific tests showing the viruses in Suffolk and recent outbreaks in Hungary may well be identical.”

It said that, along with the FSA and HPA, it was “investigating the possibility of a link” between the Hungarian bird flu outbreaks in January, poultry meat from Hungary and the “introduction of disease in the farm in Suffolk”.

Deputy chief vet Fred Landeg said: “It is important that this is investigated thoroughly, along with all the other possible routes. We are working in close contact with the Hungarian authorities and the European Commission.”

He said a possible route of infection was from imported “poultry product”.

But there were also unconfirmed reports that the investigation would focus on a consignment of part-processed turkey meat which was said to have arrived by lorry at the Holton plant from Hungary a few days before the Suffolk outbreak.

Shadow environment secretary Peter Ainsworth said: “It always seemed unlikely that avian flu arrived in Suffolk via the wild bird population, since there has to date been no evidence of infected wild birds.

“Bernard Matthews now has some very serious questions to answer about its biosecurity arrangements and the version of events it has told so far.”

Bernard Matthews said it was working closely with Defra. “We are co-operating fully and as a precautionary measure we have volunteered to cease any movements to and from Hungary.

“We want to reassure consumers that Bernard Matthews products are perfectly safe to eat.”

But in another twist, Mr Landeg said although the initial outbreak in Holton had been restricted to one turkey house, traces of the disease had now been found in three further poultry sheds. The discovery emerged from tests on some of the slaughtered turkeys.

Mr Landeg said: “All the indications are that the disease has been contained to the premises at Holton, but of course it is early days.”

The news came as the cleaning and disinfection of the Holton turkey farm was completed on Thursday night.

Two more farm workers were given the all-clear from bird flu. One vet, Gordon Young from the State Veterinary Service, had already tested negative for bird flu and seasonal flu after developing a respiratory illness.

On Wednesday a Portuguese farm worker was taken into the James Paget Hospital in Gorleston for tests, which proved negative. A third person was also tested yesterday and cleared of any serious illness.

On Tuesday, the company's commercial director Bart Dalla Mura refuted speculation that avian flu could have been brought to the UK from the Bernard Matthews sites in Hungary.

He said Bernard Matthews owned Saga Foods, Hungary's largest poultry company, but its plant was around 160 miles from where the infected geese were found.

“Our farm is about 160 miles away from the outbreak and vets agree it is just not a source of questioning at all,” he said. “There is not a remote possibility it would have happened in that way.”

On Monday, in answer to a House of Commons question posed by Norwich north MP Ian Gibson, environment secretary David Miliband played down fears of a “Hungarian connection” to the Suffolk outbreak.