At least five major supermarkets in the United Kingdom have removed gluten-free products from their shelves after it was discovered that these may actually contain gluten.

Asda, Morrisons, Sainsbury's, Tesco and Waitrose have been issued the alert from the Food Standards Agency as some of their pitta bread and pizza items may pose a "possible health risk" for people with gluten allergy. These products come from Genius, a food company with its own bakery, which may have been contaminated by a dry ingredient during the baking process, according to BBC.

The list of items include Genius Crumpets, Livwell Gluten Free Crumpets, Livwell Garlic Naan, Asda Chosen by You 4 Free From White Pitta Breads, Garlic & Coriander Naan Breads and Pizza Bases, reported the Daily Mail. Also listed were Morrisons' Free From Pizza Bases, Sainsbury's Freefrom Pizza Base, White Pitta breads, Multiseeded Pitta breads, Garlic & Coriander Naan, Syrup Pancakes and Sultana Scones, Tesco's Free From 4 Crumpets, Free From 2 Pizza Bases, Free From 4 Pitta Bread, Free From 2 Garlic & Coriander Naan and Waitrose's Gluten Free Scones, Pitta and Pancakes.

"They are a possible health risk for those with an allergy or intolerance to gluten. If you have bought one of these products and have an allergy or intolerance to gluten, do not eat it. Instead, return it to the store from where it was bought," said the Food Standards Agency in the report.

The companies have already issued an apology to its customers on their respective websites and advised the public to follow the directive issued by the agency.

Found in wheat, cereal and other baked products, gluten is a type of protein used by bakers to make the dough rise. It is believed to trigger reaction from people with celiac disease and those suffering from low immunity from gluten. Symptoms of a gluten allergy typically include migraines and vomiting.