Three students are in hospital after inhaling a 'dangerous substance', believed to have been added to an e-cigarette.
Ambulance crews were called to Saddleworth School at around 8.25am on Monday morning after a pupil became unwell.
They were then sent back to the Uppermill-based campus just before 11am to reports other children had too been taken ill.
It is not at this stage what exactly the substance is, but a statement published by the school on it's website said it was now working with police on the matter.
Students had also been warned how 'dangerous, unacceptable and potentially life changing such behaviours' can be.
The statement read: "A number of pupils have been taken ill due to the inhaling of a dangerous substance that appears to be in circulation in our community.
"The substance in question has been added in an e-cigarette. The risks of taking such substances are obvious and potentially very serious.
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"We have today met with the entire cohort concerned to re-iterate how dangerous, unacceptable and potentially life changing such behaviours are.
"By way of context, we have had to call three ambulances that could have otherwise been responding to genuine medical emergencies and accidents.
"We would call upon everyone in our community to be vigilant and work together to help us track down how this dangerous substance is being distributed to children.
"Parents and carers are asked to make it clear to their children that the consumption of such substances is harmful.
"We are working with the police to track down those responsible. If you have any information that might help us stop the distribution of such a dangerous substance, please contact Mr Casey at the school."
The ages or genders of the students involved have not been released.
A spokesman for the North West Ambulance Service said: "We were called at 8.25am and again at 10.57am to the school to reports of several people taken ill.
"We took three patients to hospital."
