Downing Street has emphasised that the onus is on the food industry to rebuild confidence among consumers after the horsemeat scandal.
"There is a job to try to address consumer confidence. That is the responsibility of the retailers and the meat industry," a Number 10 spokeswoman said.
- Institute of Grocery Distribution
- Food and Drink Federation
The results of tests on further products are not expected to be available until later in the week.
It is unlikely the exact number of people in the UK who have unwittingly eaten
horse meat will ever be known, the chief executive of the Food Standards Agency
(FSA) has conceded.
Catherine Brown said that testing was the right way to address the issue, and
said the focus would be on areas of higher risk.
But she admitted that how many people who had unknowingly eaten horse meat was
likely to be impossible to ascertain.
Sheffield Council has said it has suspended the use of all processed meat in school meals with immediate effect.
In a joint statement with caterer Taylor Shaw, it said:
Anne McIntosh, the chair of the Environment Select Committee has stated that the horsemeat scandal is a 'European problem'.
She said the committee was surprised how widespread the issue was, and that the Food Standards Agency needs to work closer with its European counterparts to solve the issue.
Ministers are now facing calls from MPs for more testing of processed meat.
The Commons Environment, Food and Rural Affairs Committee chairman Anne McIntosh described the scale of the contamination in the food chain as "breathtaking" and warned that restoring consumer confidence would take time and money.
Ministers are facing calls from MPs for more testing of processed meat amid fears that beef products contaminated with horse meat could contain substances harmful to humans.
In a scathing report, the Commons Environment, Food and Rural Affairs Committee condemned the Government's "flat-footed" handling of the horse meat scandal, saying its ability to respond had been weakened by cuts to the Food Standards Agency (FSA).
The committee said the public appeared to have been "cynically and systematically duped" for financial gain by elements of the food industry - raising wider concerns about the safety of the contaminated products.
Number 10 sources say that the Food Standards Agency raid on Farmbox Food was the result of investigations which began in mid-January. It was part of co-ordinated action by officials, agencies and the police across the UK and at a European Union level.
The owner of a Welsh meat processing plant which is being investigated for mislabelling horse as beef denies doing anything wrong.
Dafydd Raw-Rees, the owner of Farmbox Meats Ltd in Llandre, Aberystwyth, told ITV News:
Mr Raw-Rees said that he has bought the beef from the abattoir in Yorkshire, which is also being investigated by the FSA.