Four teenagers at a private school on the Gold Coast are critically ill in hospital after a suspected drug overdose.

Paramedics were called to St Stephen’s college in Upper Coomera after midday on Wednesday when seven boys, aged 15 and 14, began appearing to be under the influence of drugs.

Four boys were taken to Gold Coast University hospital in a critical condition, with another boy transported in a serious condition. The other two boys were stable when they were taken to hospital.

Police have established two crime scenes at the school and seized several mobile phones and electronic devices.

Acting Inspector Tony Wormald said police feared the boys may have bought drugs over the internet. “We’re more concerned with where they got the drugs from, why they took it and hopefully everybody pulls through safely,” he said.

Authorities suspect the substance was a powdered form of GHB, also known as fantasy.

“These boys started to become very giddy, not aware of their surroundings, one was having trouble with his consciousness, others were feeling nauseous,” said a Queensland ambulance service inspector, Patrick Berry.

“QAS do have to applaud the response from the school. It has been absolutely amazing they have been able to identify these children were deteriorating and were able to have ambulance service respond accordingly.”

Berry said it was “too early to tell” how the students would recover and toxicology results were needed to help doctors determine their course of action.

The school’s principal, Jamie Dorrington, who was reportedly attending a conference in Brisbane when the boys fell ill, joined the boys and their families in hospital on Wednesday night.

“Our primary concern at the moment obviously is to ensure their wellbeing, which I’m confident is being looked after,” Dorrington said.