European countries are expected to step up testing of food products in response to a scandal involving horsemeat falsely sold as beef, as authorities scramble to identify the source of the suspected fraud.

All companies that have handled falsely-labelled horsemeat are under suspicion, the European Union's health chief said on Wednesday, adding that the European Commission was considering strengthening EU rules on product labelling.

Ministers from the worst-affected nations will meet in Brussels later on Wednesday to discuss their response to the scandal, which erupted after tests showed products labelled as beef contained up to 100 percent horsemeat.