A policeman alerted hundreds of families to the danger-drug Strawberry Meth - despite the fact it does not exist.
Pupils and parents at 80 schools in Oxfordshire were warned of the possible risks of the fruit-flavoured drug, also known as Strawberry Quick, by the unwitting officer.
The spurious alert came after the officer sent an email via a special system connecting police and schools without checking it with colleagues.
The drug, said to contain deadly crystal meth, had apparently been given to children in sweet form by strangers outside school gates, leading to two victims being hospitalised.
But there had never been such an incident, and the officer had forwarded on an email well known for being an Internet hoax.
If he had checked with colleagues or even typed the drug's name into Google the email would have been revealed as an urban myth.
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West Oxfordshire's most senior police officer was forced to apologise over the fiasco.
Chief Inspector Dennis Evendon said: "The officer should have double checked before taking this action, which he did take with the best intentions.
"We will be making sure this sort of thing does not happen again."