Further tests for horse meat contamination are continuing as the House of Commons catering outlets were dragged into the growing scandal.
The Food Standards Agency (FSA) is to investigate a wider range of products including cafe sandwiches, gelatine, stock cubes and other beef-based foods sold pre-packed or loose.
And on Tuesday night, the parliamentary authorities admitted four beef products had been withdrawn from the heavily subsidised eateries used by MPs, peers and staff.
A Commons spokesman said the products withdrawn were steak and kidney pie, beef and onion pie, steak and kidney suet pudding, and beef Italian meatballs. He added the move was "precautionary" after one of the House's suppliers, Brakes, announced it was carrying out tests.
Tests on all four items had concluded negative for equine DNA, Brakes said.
The third phase of FSA testing, due to begin next week, will see a further 150 samples examined for traces of horse DNA, increasing the total products checked to 514 products.
The first phase saw 224 samples of minced beef products including burgers, minced beef, beef sausage or meat balls checked for horse and pork DNA, while the second, which started last Thursday involves 140 samples of beef-based ready meals including frozen, chilled or canned lasagne, chilli con carne, cottage pie, ravioli, cannelloni and spaghetti bolognese being checked for horse and pork DNA.
The sampling for the first two phases is being carried out by 28 local authorities while sampling for the third phase will be allocated to other local authorities across the UK.
The FSA expects to start publishing the results from all three phases of the study by the end of the month.
Environment Secretary Owen Paterson has said the food retail industry is "absolutely determined" to restore confidence in its products, as Germany announced that it is planning tighter controls on meat products and stronger penalties for companies that violate food-labelling rules.