Walkers has recalled some batches of crisps after rubber was found in a number of bags.
The company believes there is a chance that other bags may contain the small pieces of yellow rubber, which have the potential to be mistaken for crisps.
A range of flavours and pack sizes are potentially affected, all with best before dates of March 15, 2008 and March 22, 2008.
The Pepsico-owned snacks company is working with the Food Standards Agency (FSA) over the recall. Notices have appeared in the national press as well as in retail stores, but some of the crisps are likely to have found their way into pubs.
A Walkers statement said: "As a precautionary measure, and in agreement with the FSA, we are making consumers aware of the possible presence of pieces of yellow rubber in a small number of packets of Walkers crisps and Walkers Max.
"Although we believe the chances of finding a piece of rubber in a packet of crisps are small, we advise anyone who has bought the specified product to be alert."
The company said the potential contamination was a "highly unusual situation" which had been traced back to a delivery of potatoes. Walkers added that it is looking at options for improving detection during production.
Products possibly affected are:
- Walkers Max 50g packs - Cheese & Onion, Paprika
- Walkers Crisps standards 34.5g single packs - Ready Salted, Cheese & Onion, Salt & Vinegar, Smoky Bacon, Worcester Sauce, Steak & Onion, Marmite
- Walkers Crisps 50g 'Big Bag' single packs - Ready Salted, Cheese & Onion, Steak & Onion
- Walkers Crisps 175g pack - Ready Salted
- Walkers Crisps Cheese & Onion 14-pack, Ready Salted 14-pack, Variety 14-pack
- Walkers Crisps Cheese & Onion 26-pack, Variety 26-pack.
Supplied in Transport Ready Display Units (TRDUs): Walkers Crisps Cheese & Onion & Ready Salted 6-pack; Walkers Crisps Variety 24-pack; Walkers Crisps Variety 26-pack
Supplied in Half Opti display cases: Walkers Crisps Barbeque 6-pack
Supplied in Full Opti display cases: Walkers Crisps Salt & Vinegar 6-pack, Variety 6-pack, Ready Salted 6-pack, Cheese & Onion 6-pack, Prawn Cocktail 6-pack, Smoky Bacon 6-pack.
Anyone with an affected bag can return it for a refund. A consumer careline has been set up for enquiries on 0800 274 777.