Will eating horsemeat make me sick?
Britain's FSA says horsemeat "is not a risk in itself" but that it has ordered Findus to test its lasagne for the veterinary drug phenylbutazone, or "bute."
Bute is not allowed in the food chain because in humans it can cause rare cases of a serious blood disorder, aplastic anaemia. The anti-inflammatory was banned from use in humans after it was found that about 1 person in 30,000 recipients suffered a serious side effect.
The FSA said the levels of bute reported in previous testing of contaminated meat would have to be multiplied a thousand-fold to be at the same level as that which used to be given to humans.
In a statement, Britain's chief medical officer said: "It's understandable that people will be concerned, but it is important to emphasize that, even if bute is found to be present at low levels, there is a very low risk indeed that it would cause any harm to health."
How did horsemeat enter the food chain?
Britain's FSA said the evidence it had "points to either gross negligence or deliberate contamination in the food chain."
It said it was working closely with police, who would be involved if evidence suggested a level of criminality within the UK.
Environment Secretary Owen Paterson said the frozen burgers from Tesco and the lasagne from Findus were believed to be linked to suppliers in Ireland and France respectively.
Paterson said the French authorities viewed the issue "as a case of fraud rather than food safety."
In an oral statement to parliament on Monday February 11, Paterson said the "ultimate source of these incidents is still being investigated."
He said he had been in contact with ministers in Ireland, France and Romania and that the issue appeared to be one of "fraud and mislabeling."
AFP reported that Comigel had blamed French meat-processing company Spanghero, which blamed Romanian abattoirs where it said the meat was bought via traders in Cyprus and the Netherlands.
But Romania's prime minister said the two Romanian slaughterhouses initially suspected to have links to the horse meat scandal never had direct contact with Comigel and had not done anything illegal.
Minister of Agriculture Daniel Constantin said there was no evidence false horse meat labeling occurred in Romania.
What action are food authorities taking?
Britain's FSA has ordered food businesses to use independent laboratories to test all beef products for authenticity -- to see whether the content of the meat matches the label.
The deadline for the first round of testing is Friday February 15.
The FSA has also ordered Findus to test for bute, with results due "in the next few days" and to be published on the authority's website.
It has advised any retailers or producers that had sourced beef products from Comigel to conduct a precautionary withdrawal of product.