A substance thrown at a girl which caused a school to be evacuated amid a huge emergency response is believed to have been vinegar.

Senior teachers at The Orchard School in Canterbury raised the alarm after a pupil threw an “unidentified liquid” at another student.

Soon after, concerns arose regarding “a haze in the corridor” at the Cambridge Road site, which caters for SEN children.

Police, paramedics and fire crews arrived at the scene on September 16 after pupils were evacuated.

A schoolgirl was taken to hospital as a precaution and police spoke with a teenage boy in connection with the incident.

In an update today, the force said: “A teenage boy who was interviewed in connection with the incident has been referred to the Youth Offending Team and the investigation is ongoing.”

KentOnline understands while inquiries have not been able to establish exactly what the substance was, it is believed to be vinegar.

One parent said at the time of the incident the school told them and other caregivers to collect their children.

The mum, who did not wish to be named, added: “The whole school has been asked to pick up their kids by a text, but the school won’t tell us anything about what happened.

“Fire engines, police and the ambulance were there.

“There was someone in a white hazmat suit, and liquid was thrown over someone. It’s a major incident.”

Acting headteacher Luke Mussett wrote in a subsequent letter to parents the school had requested emergency services to attend to “offer support”.

“The two most significant incidents, one of which has been reported in the media, involved a student throwing an unidentified liquid at another student and around a similar time a concern arose regarding a haze in the corridor,” he said.

“Reacting proactively, we evacuated the secondary school to the field and kept the students out of the school building until we were sure it was safe to return.

“The fire brigade attended the school to support this.

“We are continuing to investigate both situations and are grateful the police have been able to confirm that the liquid thrown was not corrosive. We are continuing to work with the police.

“The vast majority of students coped remarkably well with the challenging circumstances and the concern around what was happening in school and the unpredictable nature of the situation.

“Those students that remained calm, supported each other and managed their emotions incredibly well should rightly be proud of themselves and their contribution to the school community.”

The Orchard School is a Foundation Special School catering for 104 pupils aged 4-18 with behaviour and learning difficulties.