Kent Police are investigating separate incidents in which three youths were taken to hospital suffering from the effects of magic mushrooms.
Magic mushrooms can leave users feeling disorientated
Staff at the Queen Elizabeth the Queen Mother Hospital, in Margate, alerted officers to the youngsters' symptoms.
Officers said the most recent case was on Sunday, 16 May.
They are now trying to find the source and supplier of the mushrooms, which become a Class A drug once they have been processed.
Insp Iain McKenzie said although magic mushrooms were not addictive, they could result in very serious illness.
Symptoms include disorientation and exacerbation of mental health problems.
He said: "We need to track down the source of these magic mushrooms before more young people end up in hospital.
"I would urge anyone with information to call me."
It is not illegal to possess or sell the mushrooms in their raw state.
But if they are processed in any way, such as being dried or cooked, possession can result in up to seven years in prison and an unlimited fine.
Supplying someone else with processed magic mushrooms can lead to life imprisonment and a fine.