Dressed in white overalls, hooded and gloved, they fillet 25 tons of fish a day, doing spot inspections for worms or parasites before the catch is frozen and shipped to stores and restaurants domestically and abroad.

FORBES: Blue Waters Gray Areas

Frozen patties in other major stores made by processing plants in Ireland and in the north of England- also suppliers to Tesco, were similarly contaminated.

FORBES: The Romanian Horse Cart Ban That's (Probably) Behind Europe's Horse Meat Scandal

Ikea has withdrawn a batch of frozen meatballs from sale in the food section of stores in the UK, and other European countries, after tests in the Czech Republic found traces of horsemeat.

BBC: Ikea store front

Last week Ikea withdrew a batch of frozen meatballs from sale in the food section of stores in the UK, and other European countries, after tests in the Czech Republic found traces of horsemeat in those products.

BBC: Horsemeat scandal: Four new products test positive

Like Wal-Mart, McDonald's has regional centers that automatically dispatch preset loads of frozen patties, napkins, chicken parts and fries to stores twice a week.

FORBES: Beyond Burgers

The Czech State Veterinary Administration said that horse meat was found in one-kilogram (2.2 pound) packs of frozen meatballs made in Sweden and shipped to the Czech Republic for sale in Ikea stores there.

NPR: Horse Meat Found In Ikea's Swedish Meatballs