Image caption The yogurts were produced by Yeo Valley for various supermarkets

Five UK supermarkets have been warned to take thousands of pots of yogurt off their shelves amid concerns they may contain pieces of rubber.

The yogurts, supplied by Yeo Valley but sold under own-brand labels, pose a possible health risk and should not be eaten, the Food Standards Agency said.

The products are sold at Asda, Co-operative, Sainsbury's, Tesco and Waitrose.

Yeo Valley said the rubber was found in a fruit conserve made by a supplier.

It said: "Whilst the risk is considered to be low, as a precaution, we will be disposing of any potentially affected yogurts that have not yet been dispatched, as well as recalling the relevant batches of products from those affected retailers."

The FSA said customers who have bought the products should not eat them.

The supermarkets are asking customers to return the products for a full refund, or contact customer services.

The products affected are:

Asda: Asda Extra Special Scottish raspberry West Country Yogurt, Asda fat free red cherry yogurt, Asda fat free red cherry Yogurt (four pack), Asda low fat coconut yogurt, Asda low fat lemon four pack Yogurt, Asda low fat lemon yogurt 450g, Asda low fat mango & passion fruit yoghurt, Collective Dairy wild blueberry yoghurt, Collective Dairy wild blueberry yoghurt.

Asda Extra Special Scottish raspberry West Country Yogurt, Asda fat free red cherry yogurt, Asda fat free red cherry Yogurt (four pack), Asda low fat coconut yogurt, Asda low fat lemon four pack Yogurt, Asda low fat lemon yogurt 450g, Asda low fat mango & passion fruit yoghurt, Collective Dairy wild blueberry yoghurt, Collective Dairy wild blueberry yoghurt. Co-operative: Co-op Rise & Shine Greek-style yogurt and raspberry, Co-Op strawberry and raspberry low fat yogurts (four x 100g), Co-op Truly Irresistible limited edition mango, Brazilian orange and coconut yogurt (150g).

Co-op Rise & Shine Greek-style yogurt and raspberry, Co-Op strawberry and raspberry low fat yogurts (four x 100g), Co-op Truly Irresistible limited edition mango, Brazilian orange and coconut yogurt (150g). Sainsbury's: Sainsbury's Basics fruit selection yogurts (2x strawberry 2x peach), Sainsbury's Basics Strawberry Yogurt.

Sainsbury's Basics fruit selection yogurts (2x strawberry 2x peach), Sainsbury's Basics Strawberry Yogurt. Tesco: Tesco Finest strawberries & cream yoghurt, Tesco low fat coconut yoghurt 450g, Tesco low fat lemon yoghurt, Collective Dairy wild blueberry yoghurt.

Tesco Finest strawberries & cream yoghurt, Tesco low fat coconut yoghurt 450g, Tesco low fat lemon yoghurt, Collective Dairy wild blueberry yoghurt. Waitrose: 125g Deliciously fruity raspberry low fat yogurt, Fragrant creamy Scottish raspberry yogurt, Multipack deliciously fruity low fat yogurt (2x strawberry 2x raspberry), The Collective Dairy wild blueberry yoghurt (450g), The Collective Dairy wild blueberry yoghurt (150g).

No other batches or products are known to be affected, the FSA said. Yeo Valley branded products are also unaffected, the company said.

A spokeswoman for Yeo Valley said: "The supplier has identified the cause and has identified all fruit conserves, an ingredient used in fruit yogurts, that may be affected.

"Food safety and quality are paramount to Yeo Valley. We are working with the Food Standards Agency and the supplier in question to ensure it does not happen again. We would like to apologise unreservedly to all customers."

Dr Lisa Ackerley, a food safety expert, said people should not worry too much if they have inadvertently eaten one of the affected products.

"The risks are probably pretty low," she said. "It's more to do with the potential for choking, so particularly for younger children.

"It's very important that you don't eat one, but if you have eaten one then it's quite likely that it would pass out of the body and it won't have caused you any harm."