Young people in Ballyclare, Antrim and Newry have reportedly fallen ill after inhaling a substance from a vape type device.
Police say there could be other unreported incidents in other areas.
The PSNI is warning parents, guardians and young people following these reported incidents.
“We would urge anyone using vape devices to only use liquids obtained from reputable sources. People under 18 years of age should not be using these devices as their sale is prohibited to anyone under 18,” said a PSNI spokesperson.