France first imposed a selective ban, and then on Tuesday blocked sales of all canned Coke drinks. But the origin of the problem - even its existence - remains hotly disputed.
The Coca-Cola company admitted to committing errors that may have caused the illness, blaming mistakes at two different plants, one in Belgium and one in Dunkirk in France. Sales of rival canned drinks have soared.
But two leading Belgian scientists said they believed the outbreak of nausea, headaches and stomach upsets, mostly among children at three Belgian schools, was more likely to be a case of mass hysteria.
The two accidents of contamination admitted by Coca-Cola should not be entirely discounted, they said, but they seemed too trivial in themselves to cause such an outbreak. The scientists said that the illness probably had a "mass psychological" cause, linked to the anxieties generated in Belgium by the dioxin poisoning of chicken and eggs.
The French government banned sales of Coca-Cola in cans on Tuesday, despite assurances that none of the drink made for the French market was affected.
A spokesman for Coca-Cola France said the company was sure that no product distributed in France had been contaminated, despite two instances of nausea reported near Dunkirk.
"The problem is essentially a Belgian problem but, in a free European Union market, we cannot be certain that products distributed in Belgium might not in some cases end up on sale in France," a company spokesman said. "In the meantime, we advise out customers to wait a little while before drinking cans of Coca-Cola that they have at home."
The director-general of Coca-Cola Belgium said earlier that the causes of the illness had been identified "with absolute certainty". Philippe Lenfant said a factory in Antwerp had used a "bad carbon dioxide" for a very brief period while producing small bottles of Coca-Cola and Diet Coke.
The factory at Dunkirk, which also produces for the Belgian market, had allowed a fungicide sprayed on wooden pallets to be smeared on the outside of some Coca-Cola cans. Although none of the fungicide had entered the cans or the drink customers might have been made sick smelling the substance.
Alternatively, they might have consumed small quantities of the fungicide as they put the cans to their lips.
However, in separate statements, Dominique Lison, professor of toxicology at the University of Louvain and Bernard Rime, professor of psychology at the same university, said the amounts of poisons involved in both cases would be too small to cause the kinds of symptom suffered by the victims in Belgium, France and Luxembourg.
They said they believed some form of mass psychological cause was far more likely, originally affecting classmates at three schools in Flanders and then spreading to other people after the outbreak was reported on the television.