Police are investigating reports the drug behind a mass overdose at a Gold Coast private school was a Russian designer drug bought online.

Four Grade 10 boys from St Stephen’s College were in a critical condition and one was serious when they were taken to hospital on Wednesday after taking what could have been an anti-depressant.

The seven boys became giddy, nauseous and unaware of their surroundings before being rushed to hospital.

Gold Coast University Hospital said the boys, aged 14 and 15, have improved but would not confirm whether four were still critical.

The other two boys were stable when they were taken to hospital, and two students have been released.

Police are still awaiting the results of toxicology reports to confirm which drug was involved but confirmed they were investigating reports it was the Russian designer drug Phenibut – an anti-depressant used to treat anxiety and insomnia – that may have been bought online.

Police fear copycat behaviour and have called for anyone still possessing the dangerous drug to come forward.

“You are always worried about copycats, people who see these things and think that’s a great idea,” Detective Senior Sergeant Greg Aubort said on Thursday.

“We do not want copycat behaviour, we do not want people seeing videos like this and we don’t want it escalating … you always have that fear that someone is going to attempt to copy.”

Senior Sergeant Aubort said police needed to account for all the drugs involved.

They have also interviewed people in an attempt to secure any video footage of the incident.

Police are working with other agencies such as the Australian Border Force and will search the boys’ personal devices to substantiate how they obtained the drugs.

“If it’s obtained from the world wide web or alternative means … we look at all of those things, the existence of the dark web we know of … we’ll try and get to the bottom of that,” Senior Sergeant Aubort said.

“This is a difficult space we live in, in terms of parents and our children who are growing and developing as individuals, pushing boundaries, looking to experiment.”

The incident has shocked the Upper Coomera school’s community, with parents of other students concerned for their children’s safety.

“I’d have to seriously consider if I leave my children at the school, to be honest,” parent Greg Peters told ABC radio on Thursday morning.

-with AAP