The Brakes Group, which supplies food to Scottish schools, admitted it had provided the tainted meal identified by food authorities during tests on school dinners at the North Lanarkshire secondary.
Scotland Excel, an agency that procures supplies for the majority of Scottish local authorities, has now sent a warning to schools to take all frozen beef products off the menu.
A spokesman for Brakes said it was contacting all of its customers and advising them to place products in a segregated area while an investigation is carried out.
He added: "On February 21 we were informed by the Food Standards Agency that a frozen beef burger had tested positive for horse DNA following a sample taken from a local-authority school in Scotland.
"Before this incident, Brakes had already received negative test results on all 127 beef products supplied to that customer. In addition, Brakes had received 32 negative tests results on products that we buy from the same supplier and they, in turn, had 28 negative tests on finished products and raw material they handle. We have a duty of care to all our customers. Until we are able to ascertain the facts, we have placed the beef burger on hold as a precaution."
A spokesman for Scotland Excel said: "We have taken the decision to recommend to all of our customers that they should take a precautionary approach and suspend further use of all frozen beef products, including frozen mince, until further investigations are completed.
"It is important to emphasise that this is a purely precautionary measure and, at this time, no other samples of frozen beef products have returned a positive result for horse DNA."
A spokesman for North Lanarkshire Council said: "It is simply unacceptable that a supplier would supply a product containing horse DNA to one of our schools. We will continue discussions with Scotland Excel with a view to ensuring we are satisfied with the integrity of food supplied to us. In the meantime, we have removed all frozen beef products from our menus across all our premises."
Martha Payne, the 11-year-old blogger and campaigner for better school meals, said: "It's terrible that horsemeat is in schools. We don't know where the horses came from and how they were looked after. We should change what we eat if we don't know what it is or where it comes from."
Opposition parties have accused the Scottish Government of being "asleep on the job" over the scandal. However, Secretary for Rural Affairs and the Environment Richard Lochhead dismissed criticism, saying: "We have made sure that as soon as a positive result was found in Scotland, people were informed and action taken."
Meanwhile, major catering firm Sodexo and frozen foods giant Birds Eye became the latest companies to withdraw beef after finding horsemeat.
Birds Eye said it was withdrawing three dishes after tests found horse DNA in a chilli con carne dish sold in Belgium. Its spaghetti bolognese, shepherd's pie and lasagne are made by the same Belgian maker, Frigilunch.
Sodexo supplies national football stadium Hampden, the Museum of Scotland, and the National Galleries of Scotland.