The latest food supplier to be affected by the horsemeat scandal is the catering giant Sodexo, which supplies schools, care homes and the armed forces.
Earlier, Birds Eye withdrew three types of beef meals from sale, and Scotland banned the use of frozen burgers in schools and care homes.
Consumer Editor Chris Choi reports.
Peter Marks, chief executive of the Co-op, wrote to more than a million of the company's members today to apologise for "meat contamination" in its products.
Two lines of frozen own-brand beefburgers, made with meat supplied by Irish manufacturer Silvercrest Foods, were withdrawn from sale by the firm after they were found to contain horse DNA.
Mr Marks wrote:
He also told members that the first 76 products of 102 own-brand products sent for testing were negative for horse meat contamination, with further results expected later.
The Co-op is to review its meat supply chain in light of the scandal, he added.
All Scottish schools have been told not to serve frozen beef burgers after one was found to contain traces of horse DNA.
Local authorities were advised to "place a hold" on the use of the products following the discovery in a burger at a North Lanarkshire school kitchen.
The measure also applies to council leisure facilities and some social care establishments.
Meanwhile, councils across the country were advised to take frozen beef burgers off the menu as a precautionary measure.
Scotland's Rural Affairs Secretary, Richard Lochhead, said it was "really unacceptable that any school child in Scotland should be eating a burger which has got horse meat in it".
Results of the industry tests on 2,501 beef products collated by the Food Standards Agency last week revealed 29 positive results, relating to:
- Aldi's special frozen beef lasagne and special frozen spaghetti bolognese
- Co-op frozen quarter-pounder burgers
- Findus beef lasagne
- Rangeland's catering burger products
- Tesco value frozen burgers and value spaghetti bolognese
- Find out more here.
The first phase of tests concentrated on samples of minced beef products being checked for horse and pork DNA, while the second phase involved samples of beef-based ready meals.
The third phase will include products marketed or labelled as containing beef as a major ingredient, including;
- beef dripping
- stock cubes
- stewing steak
- ready meals which contain beef that is not minced
The Birds Eye announcement comes as the Food Standards Agency prepares to publish the results of its latest round of industry tests on meat products later today.
Find out answers to your horsemeat questions on the Food Standards Agency website.
The three products which Birds Eye is removing from sale as a precaution after horsemeat was found in another product in Belgium are:
- Traditional Spaghetti Bolognese 340g
- Shepherd’s Pie 400g
- Beef Lasagne 400g