The Co-op grocery chain has urgently recalled 165,000 milk chocolate Santas after someone apparently inserted small watch batteries into an unknown number.

The retailer said two customers found batteries in their chocolate figures and that it was now investigating the matter.

Lithium batteries are often used to power toys, remote controls and birthday cards and can cause severe life-changing injury or even death in young children if accidently swallowed.

The working assumption is that someone “deliberately” placed the batteries inside the hollow chocolate treat, a spokesperson for Co-op told The Independent.

The chocolates that had been subject to tampering were bought at two different locations.

The German-manufactured Santas are also available from other retailers. Co-op has advised customers not to eat the treats until the issue is resolved.

A spokesperson for Co-op said: “The health and safety of our customers is our top priority. We are concerned about two separate instances of alleged product tampering involving our hollow milk chocolate Santa foil figures, which have been found to contain a small battery. As a result we have begun a UK-wide product recall.”

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The police and Food Standards Agency were notified.

Anyone who is concerned should call Freephone 0800 0686 727, Co-op added.