Five teenagers at schools and colleges in Lancaster and Morecambe were taken to hospital after smoking vapes believed to contain dangerous drugs, said police.
Police believe the vapes could have contained "dangerous Class B drugs including amphetamine and THC".
They are urging parents to be vigilant after five pupils fell ill and required hospital treatment after smoking the vapes.
Supt Craig Kelshaw, of Lancashire Police, said: "The legal age to use and purchase vapes is 18, however, we know that they are being sold to young people via social media, and these are then being taken into schools and colleges.
“Not only is this a health issue, but those possessing and supplying illegal drugs could be committing criminal offences. We are working closely with local schools and partners to share information and intelligence.
“We would also urge parents, guardians and anyone with information they may have about those supplying these vapes to call Lancashire Police on 101.”
Cllr Michael Green, Lancashire County Council's cabinet member for Health and Wellbeing, added: "We are very concerned about the latest spate of young people becoming ill after using vapes believed to have contained illegal drugs across Lancashire.
“We know that our young people are obtaining these substances often via social media and using them in school settings.
"Vaping illegal and unknown substances carries significant health risks including becoming immediately unwell, loss of consciousness and even risk to life and we urge everyone to do their utmost to be vigilant and aware of the very significant dangers."
If you are concerned about a young person using drugs and vapes, please contact specialist support charity We Are With You via their website or on 0808 164 0074.
Anyone with information about the supply or use of these illegal vapes should contact Lancashire Police on 101 or Crimestoppers anonymously online here or by calling 0800 555 111.
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