Nicolas Neykov, the head of Ferrero France, said the contamination came “from a filter located in a vat for dairy butter”, at a factory in Arlon in Belgium.

He said the contamination could have been caused by humans or raw materials.

Chocolate products made at the factory in Arlon, southeastern Belgium, were found to contain salmonella, resulting in dozens of cases in several European countries.

The factory’s closure and the health concerns were blows to its owner, Italian confectionery giant Ferrero, coming at the height of the Easter holiday season when its Kinder chocolates are sought-after supermarket buys.

“This crisis is heartbreaking. It’s the biggest removal of products in the last 20 years,” Mr Neykov said.

But the company hoped to be able to start up the factory again, with 50% of health and safety inspections to be carried out by an approved “external laboratory” in the future, instead of the previous system of only internal reviews.

“We have asked for a reopening from June 13 to relaunch production as soon as possible,” he added.