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. The revelation was made after frozen burgers were removed for testing last week.
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".
News of the discovery in North Lanarkshire emerged on Thursday night. The school where the positive test was recorded has not been named.
A local authority spokesman said: "The council has notified the Food Standards Agency, as it is required to do, and investigations are continuing. Our investigations are focusing on the use of frozen burger supplies during the past three months, the maximum length of time these would be held in storage." Samples of frozen mince came back negative for horse DNA.
Meanwhile, councils across the country were advised to take frozen beef burgers off the menu as a precautionary measure. The move was confirmed by procurement agency Scotland Excel, which deals with contracts on a national basis.
Opposition parties accused the Scottish Government of complacency and being "asleep on the job" over the horse meat issue.
Scottish Conservative leader Ruth Davidson said: "Richard Lochhead has been caught asleep on the job while one of the biggest food scares for several years has been taking place. This week, he stood up in Parliament in an attempt to give public reassurances that the Scottish Government was on top of the horse meat scandal."
Scottish Greens spokeswoman Alison Johnstone said: "The Environment Secretary seems to be all at sea on this issue and is failing to reassure the public, in particular parents whose children eat school meals. The complacency being shown by ministers is underlined by the fact that Scotland appears to spend just £1.18 per pupil per school meal."