Threats on Carrefour

Carrefour has been the victim of serious threats for weeks now. Cards with skeletons on them have been put among the goods in the supermarkets. But today these threats are getting more and more serious, a a woman brought a letter to the shop settled in Venissieux, France. This letter asked for 800 000 euros, or some people would bring poisonned food in the shop.
Carrefour is absolutely not making fun of the threat, as they increased the number of people to monitor what is going on in and around their supermarkets.

I tried to reach someone at the HQ, but no one wanted to answer any of my questions about this issue. Indeed, an enquire is on tracks, so they will let us know the result, but nothing before the official stuff!