Five children required hospital treatment after smoking vapes containing synthetic cannabinoids, also known as Spice.
Police officers were called to a school in Eltham, in south-east London, on January 29 "after a number of students reported feeling unwell".
One of the children has been put in an induced coma, the Mirror reports. Last month, two children in Merton were also left unwell after using a vape laced with Spice.
The Welsh Emerging Drugs and Identification of Novel Substances service (Wedinos) has warned that people buying e-cigarettes laced with Spice may have thought they contained cannabis oils or liquids.
Almost a third of the 196 samples of liquids submitted to them in 2023 contained a class of chemicals which Spice belongs to, they revealed.
A Met spokesperson said the force was "aware of illegal drug products being sold in vape form by illegal drug dealers" where "vape products may be described to those buying them as containing THC".
The spokesperson added it can take one to three hours for the effects of the drug to manifest.
"Our message to the public is clear. You should never buy illegal drugs since you simply do not know what these products contain," they said.
"We have been liaising with the Office for Health Improvement and Disparities about this issue."
It comes as the UK Government confirmed the ban on disposable vapes last month in England, Scotland, and Wales to tackle the rise of young people vaping.
So what is Spice, what is it made of and how dangerous is it? Here's everything you need to know.
What is Spice?
Spice is a plant-based mix of herbs laced with synthetic chemicals meant to mimic cannabis's psychoactive substances.
It has a flaky texture, green in colour and is usually smoked.
It's both strong and cheap, making it appealing to some of society's most vulnerable groups, including the homeless.
What is Spice made of?
The origins of the chemicals used to make Spice date back to the mid-90s, when American chemist John Huffman was studying the impact of cannabis on the brain.
The production of synthetic compounds involved in the experiment led to the creation of a new compound, JWH-018.
Fast forward over two decades and most Spice sold on the streets doesn't even contain JWH-018. Instead, it contains variations of it, which are both untested and unreliable.
What effects does Spice have on users?
Like cannabis, Spice can make users feel happy and relaxed, but the effects are much stronger and often unpredictable.
Users recall experiences of feeling brain-dead and paralysed, with numerous reports of people having sometimes fatal heart attacks and strokes.
Cases have also been reported of kidney damage, liver damage and psychosis.
Why is it called the 'Zombie Drug?'
Spice also goes by the name of "Zombie Drug," due to the zombie-like state it can leave users in.
The issue became so widespread that videos of people slumped on park benches and the like went viral on social media, prompting a trend of "zombie hunting" on sites like Facebook.
How is Spice different from cannabis?
Although Spice is meant to mimic the psychoactive effects of cannabis, it is not the same thing.
Although the chemicals in Spice and THC (the psychoactive compound in marijuana) act upon the same part of the brain, the chemicals in Spice can be more than 100 times stronger.
Cannabis is also sold in buds whereas Spice is a mixture of herbs.
Why are there calls for Spice to be reclassified?
The detrimental impact of Spice on Britain's communities have led police officials to take action.
The Home Office said it recognised the dangers associated with synthetic cannabinoids and was continuing to monitor their impact.
It's hoped that reclassifying Spice will make the public more aware of its risks and mean harsher sentences for dealers.
