More than 350 food products have been taken off shop shelves after they were contaminated with an illegal food dye.
Pizza is one of the items affected
The Sudan I dye, linked to an increased risk of cancer, was in chilli powder used by Premier Foods to make a Worcester sauce used in other products.
The Food Standards Agency has issued a warning advising people not to eat the products but said there was "no need to panic" because of the "very low risk".
The full list of products can be found on the website www.food.gov.uk.
Premier Foods said it had been assured the powder did not contain Sudan 1.
"It must be stressed that the product withdrawal is a purely precautionary measure, and the levels at which Sudan 1 occurs in the products concerned presents no immediate risk to health," Premier Foods said in a statement.
Dr Julie Sharp, of Cancer Research UK, said the people who had already eaten foods that had been contaminated had no reason to panic.
She said: "The risk of cancer in humans from Sudan I has not been proven and any risk from these foods is likely to be very small indeed."
The FSA is working with the industry and local authorities to ensure any remaining affected foods are removed from sale.
A list of 359 affected products, including soups, sauces and ready meals, can be found on the FSA website.
The FSA is advising that if people have any of these foods at home they should not to eat them and contact the store they bought them from for a refund.
Chairman Sir John Krebs told BBC News there "was no need to panic" but that the products needed to be removed from the shelves.
Most of the major supermarkets said the FSA had alerted them to the contamination "earlier in the week".
They had also removed all the listed products from shelves as well as any own brand products they suspected of containing the same Worcester sauce.
Sir John admitted that it had taken more than a week from the FSA being aware of the contamination until Friday's public warning.
It was first discovered in a consignment of the Worcester sauce exported to Italy.
"It has taken us a few days because we had to get together with the food industry to find out which products had the contaminated Worcester sauce in them," he said.
Further affected products may still be discovered, he added.
Sudan I, a red dye used for colouring solvents, oils and waxes, is banned for use in food stuffs in the UK and across the EU.
Since July 2003, all chilli powder imported into the UK has to be certified free of Sudan I.
Joanna Blythman, a food campaigner, said there was no excuse for a substance like Sudan 1 finding its way into food.
"But because supermarkets now control 80% of the nation's food basket, if there is a problem it spreads like head lice through a nursery."