A criminal probe has been launched following the discovery of a battery inside a Co-op chocolate Easter bunny in Nottingham. Police and the National Crime Agency are looking into whether or not the chocolate treat had been tampered with, the supermarket giant has said.

The retailers are recalling all of the bunnies, which retail for £1 ($1.26) each, from all 2,800 Co-op stores and asked their customers to return the 3,000 already sold to stores where they can obtain a refund.

The hollow milk chocolate confectionery is manufactured in Germany and does not carry the Co-op label. The investigating was triggered after a young mother from Nottingham discovered the single-cell battery in a chocolate bunny she bought for her three-year-old daughter.

Tammy-Louise Dundon, from Bulwell in Nottingham, said her daughter Sophia Wood bit the ears off the rabbit to find the battery – similar to what you might find in a hearing aid. The 26-year-old told the Nottingham Post: "If my daughter had swallowed it, it doesn't bear thinking about. This isn't just a choking hazard. It's corrosive – she could have lost her life."

Dundon added: "I was just like: 'Oh my God!' How much damage do these batteries do? I've heard kids have died from eating them. They can get stuck in the oesophagus or can be corrosive."

The National Crime Agency investigates all food tampering incidents and the Food Standards Agency has been notified.

A Co-op spokesman said: "We are concerned about one incident of alleged product tampering involving our hollow milk chocolate Easter bunny foil figure, which has been found to contain a small battery inside.

"This follows an incident at Christmas when two similar products were targeted and contaminated. As a precaution, we have begun a UK-wide product recall and have withdrawn the product from sale.

"Customers with one of these products should not eat it but take the product back to store for a full refund."

The latest discovery is the second alleged "tampering" incident involving Co-op chocolate products in the last six weeks. Before Christmas there was a national recall of chocolate Santas after batteries were found inside two of the products.