Bernard Matthews could face prosecution over sloppy biosecurity at the Holton factory in Suffolk where the avian flu virus infected turkey chicks and 160,000 birds had to be destroyed.

Unprotected waste, including scraps of dead turkey, was left outside the processing plant in breach of EU animal byproduct disposal laws.

Scientific experts believe that infection may have spread from discarded carcasses, feathers or other detritus by scavenging gulls, rats or mice and been carried to the turkey-rearing part of the premises.

The poor hygiene conditions on the premises reported in The Times last week were described in a preliminary veterinary report from the Government yesterday.

A spokeswoman at the Department for Environment, Food and Rural Affairs confirmed that investigations were continuing with a view to possible prosecution.

Bernard Matthews — which has a turnover of £400 million a year — and its trade links with Hungary remain a central focus of the investigation.

The unresolved mystery is how the lethal H5N1 virus, an almost identical strain to the infection found in geese in the Csongrad county of Hungary, arrived in Holton, near Hales-worth. Experts said that the virus match was 99.96 per cent similar.

Experts at the Veterinary Laboratory Agency are testing for the virus in meat products held in cold storage at the Holton plant. The tests can take five to ten days and are not conclusive.

So far, state vets, inspectors for the Food Standards Agency and the Meat Hygiene Service have been unable to find any specific link between the two outbreaks, but government experts believe that the poultry imports are the “most plausible” cause of the Bernard Matthews outbreak.

Hungarian officials have started a trawl through the export papers that accompanied consignments of turkey carcasses from Bernard Matthews’ subsidiary, SaGa Foods in Sarkow, and from Gallfood in Keskemet, a plant near the infected Hungarian zone, to Suffolk between January 1 and February 1.

The authorities are also looking for possible evidence of any illicit trade, or for shoddy biosecurity that allowed infected bird faeces to travel to Britain on a lorry, a boot, a wheel arch, packaging or tool — which could have led to the spread of the virus in Suffolk.

Experts at the European Commission are to assist Britain and Hungary in determining the route of the avian flu strain that has killed at least 166 people worldwide since 2003 — when it first appeared in Asian poultry.

Raw meat that was sent to Hungary from Bernard Matthews since the bird flu was confirmed on February 3 is also to be tested for the virus. The meat had been kept in cold storage and was not being allowed into the food chain until further checks were made, Hungarian sources said yesterday.

Despite the mystery over the virus transmission and biosecurity lapses on the farm, Bernard Matthews has been given approval to resume exports to Hungary. The company, however, has decided to continue its voluntary suspension of trade with Hungary.

Problems with gulls feeding from open waste bins was first raised with Bernard Matthews management last year by its own firm of pest controllers. They had also identified holes and openings in rearing sheds that could easily allow a bird or a rodent to mix with chicks and for water or bird droppings to get into enclosed units.

Meat Hygiene Service records also reveal that inspectors issued warnings about a range of “deficiencies and noncompliance”. Though not specified, they are also related to possible breaches of animal byproduct regulations.

Bernard Matthews was served another warning last month about problems on the site. Pest control reports on January 10 and January 24 noted that gulls were carrying meat scraps half a kilometre away and then roosting on the top of the farm sheds. Poly-thene bags containing meat products and residual liquids were also thrown into the open bins and were easily blown across the site. Birds or rats may also have infected wood shavings that are stored outdoors and used to refresh bedding inside the sheds.

The virus may also have been introduced into sheds on contaminated footwear or clothing. After the disease was confirmed in turkeys in one shed it is possible that staff may have spread the disease to three other sheds on the site.

This catalogue of biosecurity failures is in stark contrast to the glowing appraisal of the company by Bernard Matthews himself. Mr Matthews spoke this week about his pride in his business, which he said had always abided by EU rules.

He denied that the company had acted evasively since the outbreak and said: “There has been absolutely no cover-up at our end. I’ve been upset about allegations that we may have withheld information. That is completely untrue.”

In a further statement the company welcomed the government report, saying it showed that the company had always acted legally.

Chris Huhne, the Liberal Democrat rural affairs spokesman, said: “This report high-lights serious biosecurity lapses at Bernard Matthews’ plant in Suffolk. Allowing wild birds to feed on raw poultry meat left in the open is highly irresponsible as it could lead to widespread contamination. The impression is still of an organisation in denial about the seriousness of events at its plant.”

Conservation experts are waiting to see whether the virus has spread into wild birds.

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