Beef burger meat bought at a supermarket in France is suspected of being behind an outbreak of e-coli bacteria.
Five children are in a serious condition in hospital in the northern city of Lille.
The supermarket is part of the German discount chain Lidl.
But officials say the outbreak does not appear to be related to the e-coli strain that has killed 37 people and left thousands ill in northern Germany.
The suspected beef burger meat has been recalled.
One man returning meat said he was giving back everything with the mark Steaks Country, to be sure there is no problem, even something he started to eat the day before.
A woman outside the store said: “It’s worrying. I’m checking the children when they go to the toilet.”
Another woman said: “Between cucumbers, tomatoes, this and that, what are we going to eat? We’re going to end up with nothing to eat in France.”
The supermarket chain says the beef used in the suspect boxes had been bought from a French supplier, but it could come from numerous countries.