The Food Standards Agency (FSA) is waiting for the Hungarian authorities to confirm the origin of the meat. Bernard Matthews is voluntarily holding the products at two cold stores to keep them out of the food chain.

There is a "remote possibility" the products contain meat from a restricted zone in Hungary which would make them illegal for sale in the UK, according to the FSA. The watchdog said the turkey products did not pose a food safety risk.

Bernard Matthews has voluntarily agreed to temporarily suspend movements of frozen products containing Hungarian meat for 48 hours, the firm said.

The FSA said: "We can confirm that Bernard Matthews has agreed temporarily to hold on to some turkey products currently held in bulk in cold stores in Chesterfield and Holton to stop them entering the food chain.

"This is not because of any food safety risk - FSA advice on this remains the same, that properly cooked poultry is safe to eat - but because there is a remote possibility that some of the meat may have come from a restricted zone in Hungary which would make it illegal to go into the food chain."

The first consignment of turkeys arrived at Bernard Matthews' Holton plant on Tuesday after the Government gave it the go-ahead to restart operations. Bernard Matthews stopped movements of poultry to and from Hungary last Thursday.

The firm said its temporary block on the movement of the products containing Hungarian meat was brought in on Tuesday morning and would last until 6am on Thursday morning.

"Bernard Matthews wants to make it clear that consumers have been reassured by the FSA that avian flu does not pose a food safety risk to UK consumers and properly-cooked poultry is perfectly safe to eat," its statement said.

Bernard Matthews said it was continuing to assist the FSA's and Defra's investigations into the avian flu outbreak.