Experts may never get all the pieces to the puzzle and might have to draw a conclusion on the “balance of probabilities”, Mr Landeg told the BBC. But he conceded the evidence suggests the virus may have travelled from Hungary in meat product rather than entering the farm on a wild bird as initially thought.

Environment Secretary David Miliband and a Bernard Matthews spokesman had previously ruled out any link between the Hungarian outbreak and the virus reaching Suffolk.

Mr Landeg said: “What we are in the middle of is a very complex epidemiological study, it is rather like a jigsaw puzzle. We are putting it together. We may not get all the pieces and we may have to come to some conclusion on the balance of probabilities.” He went on: “However, as we put that evidence together, it appears that the virus from Hungary may well be identical to the Norfolk strain and that suggests the virus was carried here directly, possibly in meat product, rather than wild birds at this stage but we are still keeping an open mind.”

Other transmission routes are still possible but Defra is “focusing” on the movement of product from Hungary at the moment, Mr Landeg added. He also said biosecurity at the plant was “reasonable” but there can “sometimes be failures or possibly some faults” in the buildings on such large premises.

Mr Landeg also told GMTV that the virus had “probably come directly from Hungary to the UK” rather than via migratory birds. Evidence given to Defra on Thursday and advice from the Veterinary Laboratories Agency indicated the virus in Holton was almost identical to the Hungary virus, he said.

It was claimed on Thursday night that a consignment of dead turkeys from a Bernard Matthews-owned plant in Hungary could be the source of the outbreak. The Observer [a highly respected UK newspaper] said the consignment, which had been partly processed, was brought by lorry to the UK, arriving a few days before January 27, when the first signs of illness were spotted in turkey chicks at the farm.

The Government has known about the contaminated meat since Monday but did not tell the public, the paper claimed. But Mr Landeg has denied a Government cover-up, telling Sky News: “We have not sat on the information.”

See also http://news.bbc.co.uk/1/hi/uk/6345521.stm”