A group of school students collapsed after taking the 'zombie drug' spice sparking a warning from police.
Cambridgeshire Police confirmed a "small group" at Thomas Deacon Academy in Peterborough had inhaled the substance via an electronic vape.
Spice is a synthetic cannabinoid with mind-altering chemicals which is typically smoked- and can be up to 200 times the strength of normal cannabis.
Known as 'fake weed', the National Institute on Drug Abuse said the health effects can be "unpredictable and dangerous".
Officers have now issued a warning to every secondary school in Peterborough which has been sent to parents following the incident earlier this month.
It informs them that there were "several reported incidents of students 'collapsing' and requiring medical attention" after taking the Class B substance.
They said anyone who has any "concerning symptoms" must be referred for immediate medical attention.
A police spokeswoman said: "An investigation into how the students came to be in possession of the substance is ongoing."
Rick Carroll, principal of Thomas Deacon Academy, said: "The academy has an extremely robust drugs policy and we work closely with partner agencies to educate young people about the consequences and risks of drug use and misuse.
"We are aware that a very small number of our students had involvement with an illegal substance and also of a similar incident involving another school.
"We dealt with the situation swiftly and are in regular contact with Peterborough police.
"To reinforce our policy on drug use and misuse, we will be running additional student sessions and assemblies after half term."
