A five-year-old boy was rushed to hospital after ingesting a 'hazardous substance' in school and suffering burns to his tongue.
The pupil had blisters appear in his mouth and was taken to the Royal Stoke University Hospital for treatment.
Firefighters, paramedics and police all attended the scene at roughly 1.30pm on February 10.
It has been confirmed that the student had consumed an 'unknown' substance and is currently in a 'stable' condition, Stoke-on-Trent Live reports.
Parents arriving to collect their little ones at the end of the day were stunned to find fire engines blocking Rookery Lane and the main entrance to the Stoke school locked.
They were instead told to collect their sons and daughters from the hall.
Staffordshire Police have now launched an investigation to understand the full circumstances of the incident at Oakhill Primary School, but confirmed it was not 'malicious'.
A spokesman said: "Police were called at 1.43pm to Oakhill Primary School on Rookery Lane, following concerns over the welfare of a child.
"Officers attended along with paramedics and crews from Staffordshire Fire and Rescue Service.
"A five-year-old boy had sustained burns to his tongue after ingesting an unknown substance.
"He was conveyed to hospital by the ambulance service where he remains in a stable condition. Inquiries are continuing.
"There was no wider risk to any other pupils or any malicious circumstances in relation to the incident."
Staffordshire Fire and Rescue Service sent the hazardous substance team to the school, along with two crews from Newcastle and one from Longton.
A spokesman said: "Firefighters were called at 1.34pm to Oakhill Primary School following reports of a hazardous substance being ingested.
"Upon arrival, firefighters found a five-year-old boy with burns and blisters to mouth area. He was taken to hospital by ambulance.
"Fire crews remain at the scene along with officers from Staffordshire Police."
A West Midlands Ambulance Service spokesman said: "We were called to reports of a medical emergency at Oakhill Primary School on Rookery Lane at 1.29pm, one ambulance and a paramedic officer attended the scene.
"We treated a young boy at the scene before taking him to Royal Stoke University Hospital for further assessment."
One mum said she arrived at the school to find several fire cars and engines and the police's tactical support team blocking the lane.
She added: "The main gates to the school were locked and blocked off and children had to to be collected from the hall and not the normal areas
"I just got a little annoyed because the school hadn’t told us what was going on."
Oakhill Primary School declined to comment.
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