An investigation is under way after children and staff at a school summer camp were exposed to a harmful gas leaving 26 people in hospital.

Patients included 10 children who were at the Barracudas summer camp at St Catherine’s School, in Cross Deep, Twickenham, when the incident unfolded.

They have since been released from hospital and a health and safety investigation was launched.

Emergency services, including 14 fire engines, were called to the school on Wednesday morning following reports of a chemical leak.

Staff and more than 150 children were evacuated from the school and punters at a nearby pub were told to stay inside.

It later emerged two chemicals had mixed as maintenance work was carried out in the swimming pool area, causing the release of chlorine gas.

Emergency services were alerted just after 10.35am when people in a changing area next to the pool smelled fumes.

Simon Brownings, Kingston fire station manager, said those taken to hospital were admitted as a precaution after complaints of runny eyes.

The Health Protection Agency (HPA) and NHS Richmond were at the scene to help with the fire service investigation.

Dr Barry Walsh, of the HPA, said, “Twenty-six adults and children who were exposed to the chlorine have received hospital treatment, however, none of them had severe symptoms.

“Exposure to chlorine can cause a burning sensation in the throat and eyes and more substantial exposures can lead to coughing or breathing difficulties.

“We are working with the NHS to ensure that GPs are aware of this incident should they take any enquiries about it."

Paramedics took nine patients to West Middlesex Hospital, three to Ealing, six to St George's and eight to Kingston Hospital.

A spokeswoman from the summer camp confirmed all patients were released from hospital during Wednesday afternoon and evening. She said: “Everyone is fine."

The summer school continued its activities just after noon when the school was given the all-clear.

Headteacher, Sister Paula Thomas, spoke of how the incident unfolded.

She said: “Everybody's absolutely fine and everything's back to normal.

"It was very unnerving seeing everyone arriving.

“The paramedics said they [the children] were all fine but would take some of them to hospital to check them out.”

Staff and drinkers at the nearby Alexander Pope hotel were told to stay indoors by police while investigations were carried out.

Manager Erica Wiles said: "The emergency services all descended [on the scene].

"I'm just amazed it was to do with chemicals.

"It was all a bit chaotic but the kids seemed to be ok."

Pope’s Grove was cordoned off by police while fire crews dealt with the incident. It re-opened shortly after noon.

A spokesman from the Health and Safety Executive confirmed it was aware of the incident and had started to make initial inquiries.

Were you or your child affected? Tell us by emailing jkilvington@london.newsquest.co.uk or call the newsroom on 020 8744 4272.