TWENTY six children had to be treated by paramedics at a primary school in Coalpit Heath on Monday, in what emergency workers first suspected was a chemical incident.

Around 20 ambulance, fire and police crews descended on Manor Primary School at 1.15pm after two pupils fainted and others complained of headaches, nausea and feeling sick. It was feared there had been a gas or carbon monoxide leak but all were ruled out and the outbreak has now been put down to a mystery bug.

Head teacher Hilary Eade said: "We had several children feeling unwell and we sent one child home. Another child fainted a bit later and was having difficulty breathing so we called an ambulance. In the length of time it took them to arrive there were other children in a similar state and we thought maybe there was more to it.

"Paramedics contacted the incident team and police closed the road and the building was cleared. Everyone was fine but I knew seeing all the vehicles outside that some people would be concerned naturally."

In total, eight pupils were sent home and a further 18 became ill - more than 13 per cent of the 202 children at the school.

Pupils were held on the school playing fields while parents were sent a text message calling them to wait at the nearby Minors’ Institute while rigorous safety checks were carried out.

Avon Fire and Rescue Service sent seven appliances including four fire engines and two chemical hazard teams and experts carried out carbon monoxide tests on the buildings and several pupils.

A Fire and Rescue spokesman said: "We went into the school with chemical detection equipment just to see if there were any hazardous substances. The school has been ventilated and we carried out full checks but did not pick up anything hazardous."

Pupils said it had been a frightening experience. James Cleaver, 10, said: "One person fainted and about 10 minutes later another person fainted. "I was a bit scared but just played with my friends on the field while we waited."

Abigail Dennington, also 10, said: "It was just a bit scary being there and seeing all your friends falling ill."

Parents spoke of their concerns as the dramatic scenes unfolded.

Rachel Flowers-Brine, whose nine-year-old daughter Molly attends the school, said: "I got one text message and didn’t panic, then I got a second one and I panicked.

"I came up here and saw seven fire engines, ambulances and everything but I knew she would be fine because she is as tough as boots."

Mark McKay, whose son Archie, seven, was at the school, said: "It could have been a lot worse. I don’t think it was that serious but they are not taking any chances and that is the way it should be."

John Oliver, from Great Western Ambulance Service, said paramedics had handed out letters to parents and staff assuring them that children were safe and providing advice should anyone become unwell. He said the eight pupils who had gone home were visited by paramedics on Monday afternoon and were given the all-clear.

"This was a very good example of getting the right resources to the scene so people could be checked over there, which was far less stressful for them and did not result in lots of people being taken to hospital," said Mr Oliver. "No pupil was considered seriously ill in what could have been a very serious incident."

The school reopened as normal on Tuesday, although some parents opted to keep their children at home for an extra day.