Worcester Sauce crisps are among the recalled products
The colouring involved in the largest recall of food products in UK history has been banned from food in the EU for two years, so how did it find its way on to British supermarket shelves?
Chilli powder containing Sudan I, a dye linked to an increased risk of cancer, was used in Worcester sauce that became an ingredient in hundreds of other products.
It is thought the original chilli powder was imported before regulations banning Sudan I were introduced in 2003.
Jenny Morris, policy officer at the Chartered Institute of Environmental Health (CIEH), said since that time there had been a "very robust system in place for importing chilli".
"It [contamination] shouldn't happen now in that every quantity of chilli that comes into this country, because there is a known risk, is required to have an analyst's certificate," she said.
Any batch without a certificate is detained for sampling and analysis.
The Food Standards Agency (FSA) and local authorities also randomly test more than 1,000 consignments of imported chilli products a year, and all those containing Sudan I are destroyed.
"If you stop it at the point of import, that is much easier than trying to chase it all round the country," Mrs Morris said.
She added that the number of products involved in the current scare was "really testing" the systems in place for tracing the source of contamination and recalling food.
"Unfortunately it is only when it really happens, that you really test it.
"Every time you get a contamination, you need to look at your system and see if adjustments need to be made."
Tim Lang, Professor of Food Policy at City University, London, said the contamination "suggests there is still inadequate routine testing" of food in the UK.
The chilli powder was traded between three UK firms, then went on to be used in dozens of retailers' soups, sauces and ready meals, but it was not until a consignment of Worcester sauce was exported to Italy that the contamination was spotted.
"What the Sudan I case shows is that in an increasingly global food supply chain, safety controls need to be global and they are not," Prof Lang said.
Food businesses in the UK are legally bound to take "all reasonable precautions" to ensure food they put on the market is safe.
SUDAN I FACTS
Red dye used in solvents, oils, waxes, petrol, and shoe and floor polish
Tests on rats have shown it can cause bladder and liver cancer
Has been found in some chilli powder imported from India
Illegal to add it to food in the UK and rest of EU since 2003
An FSA spokeswoman said that, in response to the current scare, it would "conduct a critical review to establish what further measures and actions may be required of food companies to ensure that the food that they sell is safe and fit for human consumption".
Prof Lang added that the Sudan I contamination should serve to highlight the many additives it is legal to add to food.
"This illegal adulteration has exposed the routine acceptance of legal adulteration of food," he said.
"British people eat food routinely that is stuffed to the top with colourings and flavourings designed to make industrial food acceptable."